When I first started stock illustrations the sites mainly catered for photographers. Now that most of the sites support vectors there might be a few hidden Gems that you have missed off the usual beaten track.
So from the kindness of my heart and the lure of getting rich from riding on the back of the earning from all your affiliate referrals

I am willing to share my little secret sites!
Sites that are aimed at mainly vector artist:
VectorStockGraphicLeftOversClipArtOf Please mentions nicemonkey on the referral section
Main Stream sites that accept vector submissions
FotoliaShutterstockiStockCutcasterYaymicroCrestockZymmetricalDreamstimeBigStockPhotoCanstock123RFFeaturePicsStockexpertHopefully this list will be a help to someone, Please feel free to add any sites I have missed.