I would agree with Dan, and let the experts have a look and your failed images.
If a site rejects your images it is not personal so don't give up, but look to resolve the problems by making it a goal, a few months of self learning stock photography will raise your game more than anything else, only if you are prepared to take advice.
Don't worry to much about getting images uploaded and sales, but focus on getting them right first the rest should follow, SS and IS have good critique forums where you can look at other contributors rejected images and learn a lot from them as well
When I started I had loads of "good images", but when I understood the quality requirements I struggled to find enough to use as acceptance images, so it was back to looking and learing and basics.
I knew they were "Good Images" because my friends and family said so, and now they think they are "Just Fantastic"

David