I don't know if there are that many services out there for realtime 3D on the web, but one way to get a more in-depth level of scrutiny for critiques would be to use a service that would allow people to see your model / animation loop in realtime in the browser. Since this is geared towards a low-spec sort of hardware, I don't think performance of a 3D java or flash applet would be impacted that greatly by the detail in the models.
This way people could see the model, rotate it around, maybe see a looping animation if there's one available, and even check out the wires and shaded and unshaded versions. I know there are some sites that are trying to be "like youtube, but for 3D objects" type of sites. perhapse embedding one of those (if that's possible) might be a servicable alternative to distributing the actual files. it would probably aid in file-format issues. You'd probably end up with people asking constantly how to open 3ds files in whatever app all the time if youu started distributing the files. I think it would be best to avoid as much as possible the software-specific issues that tend to pop up on a lot of 3D sites.
Anyway, I'll do some googling and see if I can suggest a service as well. I've always been more deeply involved in 3D modeling and animation than pixel art, and I'll probably make more use of this section than any other section in here, now, as far as posting goes. This could destroy my lurker status.