yep, to echo what Cjphoto said.
don't hold your breath on alamy rejecting anything.. as long as your technical specs are in order they will accept EVERYTHING. So you have to have to make the decision what you want where first.
I genearlly decide by, things with low sales potential I send to alamy, because there will only be a few people who want the image, then I may as well sell it high. High sales potential - the micros. There are so many images on alamy it is hard to get sales no matter what images you have good or bad. I think my best chances on there are the ones with the low sales potential, which also happen to be more rare type images that not many other people have and not many other people want.
To submit to... start with Istock, fotolia, shutterstock, and dreamstime and see how you like it. Istock DOES have really good sales if you can get images accepted there and you feel like spending the time uploading. shutterstock is perhaps the best in my opinion and then fotolia and dreamstime are about equal.