(example of one image submitted this year)
I want now to give away one of my small 'secrets'. This I employ sometimes before submitting.
I make a search on, say: red peppers. I want to see results for the most downloaded from the top sellers down (one to four pages) and then compare if my image fits in there as something really different and new. If yes, is definitely worth to submit. If not, depends. Maybe I can submit anyway if I think my image is somehow better than one already there. But... only if that topic-subject is not too well covered yet in Dreamstime. Otherwise is a sure Not-to-submit situation.
I underline again: check your images against the ones that are already on sale. This will avoid also the chances of rejections for: 'this is well covered subject' or 'we don't need this kind of images'.
P.S. For who is thinking 'what the heck is acceptance ratio'? Here the very brief description: the ratio of images accepted every month. More images accepted=higher the ratio. Higher ratio means you are a 'higher quality' photographer. That has practical results: more sales, probably your images will appear higher in searches, more chances to be chosen as photographer of the week and so on. Just good thing happens when you have high AR.