I just started uploading to PhotoDune and must say I am disappointed so far.  I realize the site is new, in fact still marked "beta" so Envato if you are listening here are my suggestions for improvement:

1) Approval seems to be taking about a week.  I am at 8 days on my oldest batch.  This is not terrible, but not good either,  I appreciate a site that can turn my images in 3 days or less.

2) Inspection, or inspectors seem a little random and worse, much too eager to reject for: "Unfortunately we're not able to accept your submission at this time as it does not meet our general requirements. Images must be well composed, technically and aesthetically sound, and provide utility for potential buyers."  I have no issues with rejections for quality or if you just do not want that image, it is your site.  I do take issue when an inspector decides there is no value to any of the millions of potential buyers all by themselves.  Most of the images rejected were accepted at other sites, and some have already sold.  Again, not a complaint, I send the same images to all 6 agencies and they can take what they want.  But for a new site, I hate to see you go down the Low Commercial Value route.  If it is a good clean image give it a chance please.

3) Errors for having too many keywords.  Probably the most irritating thing on the site.  I get you only want 50 words, I disagree that 50 is the right number, but it is your site.  But why on earth do make us manually figure out how many keywords there are?  If you know it is over 50 then obviously you counted them, right?  Then put the silly number on the screen.  Do you have any idea how much time I have wasted trying to figure out which ones to delete and get to 50? Without knowing how many I need to delete?  Silly, Silly, Silly.  That time should be spent creating images not counting keywords.

4) The site appears to have been designed with a far lower number of items in mind.  The list for "currently processing" on my dashboard stretches for pages, and I am only uploading a few at a time.  My portfolio is tiny and it seems cumbersome, I cannot imagine how folks with a real portfolio are getting along.  Again, not a complaint, just a suggestion that if you are going to be a stock photo site, you will need a little different look than what works for some of the other items you sell on your sites.  How are you going to handle 20 million images?

5) Acceptance/rejection emails.  Is it possible to get them in a single email?  Maybe there is a setting for this and I missed it.  I only upload 25 at a time but getting 25 emails is still a bunch and those sending 100's or 1,000's of images must be deluged.

Thanks for listening.

All you say is truth, and the keyword count issue is indeed the most annoying problem for me.

For those wondering about rejections there, no improvement.

1) Approval seems to be taking about a week.

Annoying but not a big drawback for me.

2) Inspection, or inspectors seem a little random and worse, much too eager to reject for: "Unfortunately we're not able to accept your submission at this time as it does not meet our general requirements. Images must be well composed, technically and aesthetically sound, and provide utility for potential buyers."  I have no issues with rejections for quality or if you just do not want that image, it is your site.  I do take issue when an inspector decides there is no value to any of the millions of potential buyers all by themselves.

This is a deal-breaker.  Especially if I'm submitting a  'niche' image that is already on 3 major sites and does sell now and then.  I have a very small portfolio and if they reject my best sellers, there's no point.

3) Errors for having too many keywords.  

Agreed.  No one is going to bother going through all their images, counting keywords and hand-editing the list during submission.   Fortunately most of my images don't have that many keywords, if they did I wouldn't submit here.

4) The site appears to have been designed with a far lower number of items in mind.  

True, but not really a problem.

5) Acceptance/rejection emails.

True, but not really a problem.

For me the big disincentive to submit more here is the low prices.  At this time I'm waiting for indications that the reviewing has stabilized and is making sense; but even if it does I'm undecided. Do we really want to support this agency, which seems to be based on subscription prices for on-demand sales?  

Who cares...