There are no limits on the number of images you can upload.  Site offers, ActiveX controlled Multiple Uploads as well as an FTP option. Or if you would like to suffer through HTTP version, that is available as well.

Commissions on this site are $0.25 however, the price structure has changed a bit. 

Here is the breakdown of how it works.
$0.25/image if your earnings are less than $500
$0.33/image if your earnings are between $500-$3000
$0.36/image if your earnings are between $3K-$10K
$0.38/image if your earnings are more than $10K

Those total earnings mentioned above are for lifetime earnings which means that, from the time you started until today.

Also, if you refer someone to the site and if they get accepted to start selling images, you will be given a $0.03 referral for each image they sell.  (Shutterstock has the best referral program in the industry so far)

In May 2008, Shutterstock (SS) has added an On Demand feature where the buyers pay for each image they purchase instead of subscriptions.  And the pay outs for this is more lucrative.  How much? well, here it is

Here is the breakdown for SMALL and MEDIUM SIZE
$0.81/image if your earnings are less than $500
$1.07/image if your earnings are between $500-$3000
$1.17/image if your earnings are between $3K-$10K
$1.24/image if your earnings are more than $10K

Here is the breakdown for Any Size
$1.88/image if your earnings are less than $500
$2.48/image if your earnings are between $500-$3000
$2.70/image if your earnings are between $3K-$10K
$2.85/image if your earnings are more than $10K

Also, there is another service that they offer that is called Enhanced License which is the best value for both the buyer and the seller. Any image you sell with an enhanced license means that the contributor (which is you) gets $28.00 per picture.

FTP Upload:  YES
Limited Upload: NO
Ease of Upload Process: 4 (1 hardest, 5 easiest)
Editorial: YES

- My Portfolio

Based on your tenure and approval rating there are limits for the uploads.  This site offers one upload at a time. Unless you download their software that is called DEEPMETA, than you can batch the pictures and the software takes care of it.

Either ways, this is the only site I HATE, absolutely HATE uploading my pictures because the upload process is tedious, and if you are not exclusive, your sales are going to be rather Hit and Miss.

Commissions are anywhere between $0.10 (which is rare) to $3.00 depending on how . 

If you are new and planning on submitting to more than one site, my suggestion to you is to upload here when and if you have extra time.  If you are not exclusive, it is a waste of time, unless you have the patience to upload 10 pictures a week, until you sell 250 pictures.  And then, you can upload 15 pictures a week, and so on and so on...

FTP Upload:  NO
Limited Upload: YES
Ease of Upload Process: 1 (1 hardest, 5 easiest)
Editorial: NO

- My Portfolio

You can upload your files without limits.  This site offers FTP option to upload the images.

Commissions on this site are 50% of sales.  Sales are sporadic on this site.  Upload process is rather easy so I do upload to Bigstock as much as I can.

FTP Upload:  YES
Limited Upload: NO
Ease of Upload Process: 4 (1 hardest, 5 easiest)
Editorial: YES

- My Portfolio

Based on your approval rating there are limits for the uploads. 

This is the only agency that lets you sell the full rights of your images, if you opt in.  How much?  Well, it depends on what you choose.  You can let the site default which is $350 if you have no uploads for the picture, and it goes up all the way to the thousands depending on how many sales you have on that particular picture.

Commissions on this site are 50%.  

FTP Upload:  YES
Limited Upload: YES
Ease of Upload Process: 3 (1 hardest, 5 easiest)
Editorial: YES

- My Portfolio

You can upload your files without limits.  This site offers FTP option to upload the images.

Commissions on this site are 50% of the sales prices.  you can make anywhere between $0.50 to $5.00 per images depending on the size.  However all subscriptions are $0.30 per iamge

FTP Upload:  YES
Limited Upload: NO
Ease of Upload Process: 4 (1 hardest, 5 easiest)
Editorial: NO

You can upload your files without limits.  This site offers multiple uploads (12 maximum at one time.)

You can contact the site admins for FTP access.

Commissions on this site are 35% for small images, 45% for medium images, 55% for large images. Images are €2.00 for small images, €4.00 for medium images, €6.00 for large images

FTP Upload:  YES (if you ask for it)
Limited Upload: NO
Ease of Upload Process: 3 (1 hardest, 5 easiest)
Editorial: NO

- My Portfolio

You can upload your files without limits.  This site offers FTP option to upload the images.

Commisions are based on two criterias.  

• If it is a Member Download, then you receive $0.50 for small, $0.75 for medium, and $1.00 for large.
• If it is a Guest Download, then you receive $1.00 for small, $1.50 for medium, and $2.00 for large.
  

FTP Upload:  YES
Limited Upload: NO
Ease of Upload Process: 5 (1 hardest, 5 easiest)
Editorial: NO

- My Portfolio

You can upload your files without limits.  This site offers FTP option to upload the images, as well as HTTP and Flash upload which is similar to the ActiveX upload process, which means EASY EASY process.

Commissions on this site are based on how many downloads you have, which determines your rank and your rank determines what you can charge for your photos.  However the subscription sales are $0.32, and each subscription sale counts as 1/4 of a sales when it comes to ranking.  In other words, if you sell 10 pictures via pay-as-you-go, and 16 subscription sales, your sold files that affect your ranking is 14 (10 + 4). 4 comes from the 16 subscription sales

FTP Upload:  YES
Limited Upload: NO
Ease of Upload Process: 3 (1 hardest, 5 easiest)
Editorial: NO

- My Portfolio

You can upload your files without limits.  This site offers multiple uploads via HTTP, ActiveX, etc as well as FTP.  My motto is, if they have FTP option, then anything else is just a waste of time.

Commissions on this site are $0.36 per subscription sales, and higher commission if you sell pay-as-you-go, but as I mentioned before, it is a bit too complicated.

FTP Upload:  YES
Limited Upload: NO
Ease of Upload Process: 4 (1 hardest, 5 easiest)
Editorial: NO

- My Portfolio

- My Portfolio
- My Crestock Page

Once you submit, there is no categorizing... Sales do not happen too often but I like the upload process.  I use the FTP and then I am done.  This site doesn't generate much income, but while I am sleeping I upload so I'm not really wasting my time. 

FTP Upload:  YES
Limited Upload: NO
Ease of Upload Process: 5 (1 hardest, 5 easiest)
Editorial: YES

- My Portfolio