The pictures you provide are really good, and its great you are providing them for free (especially for researchers without a lot of funding...). I'm using them for something totally different (psycholinguistic research with eyetracking), but they suit my purposes very well. I wish I could contribute back, but I'm only beginning to use vector graphics, so animals are still quite difficult. I do have a fair amount of everyday objects though, but I guess they don't belong here. Maybe one day we will make them available to the community in some way (although we'd have to check copyright issues first).
Garance