first, I have a higher acceptance rate at F than SS, so combined with the fact that the 1st 10 face higher scrutiny, you're going to have to be rigorous with reviewing your own work.

I looked at a few of your image (not going through 300). Some of your isolations weren't sharp and/or didn't have white backgrounds.

My advice, load each of your images at 100%. Scratch any that aren't perfectly sharp. Scratch or fix any isolations that that aren't perfectly white.

Out of what's next, look at your best sellers at F and pick 10 that show a good variety and pop the most at thumbnail size.

I'd have a look at your images, but FT is too slow. I'd like to help you - as would others - but you're going to have to put in some effort to make this easy for us to do.

May I suggest you select a few candidates and post (400 px wide) thumbnails here?

Yeah, I'm going to start using a light tent for all of my shots. I never realized that it would be that important.  And I've attached three images that I think are okay(Fotolia accepted them). Hope this helps.

Whiz...  some great advice already given...  SS is a tough one to get onto,  most folks are shot down 1,2,3 and even more times before finally getting on. Don't give up. 
     As said,it is difficult to tell from looking at a thumbs on FT, not to mention, time consuming (FT seems to run slower every time I look at it, LOL), but with the 3 you posted here, I agree with  dbvirago, that lemon is soft.  SS is going to be looking for very clear and crisp at 100. The white must be pure and solid.  The single on-cam flash is causing blown highlights & flash burns on some of your FT pix that will never get by SS. How do I know?  Been shot down for all of them... by SS.  I am a horrible isolated shootist.
     I looked at your landscape and animal shots.  I know Yingyang mentioned that they are not big fans of nature shots at the start. That seems to be true.   However,  I got on with landscape and nature shots...  I only say this if you keep having a problem with the isolated shots.  If you get rejected again,  take your very, very best, nice and crisp and rich animal shots or your 'outside/naturally lighted' object shots and give them a try.  Also, take note of what SS did/will accept and recycle those images on the next try.
     My personal experience, SS has been toughest second only to IS in acceptance ratio.  Don't give up, once you're on SS, you will be selling like crazy.  They are picky about what they take, but what they take, they also sell!!      -tom