I working in solidworks, I can upload Solidworks file, but cant upload renderings jpg files,
you want to upload the renders here?? if so it could be that the resolution is to low or to high try to change the resolution. for instance the standard in inventor is 640x480 and aparently that is to low for this site when i uped it to 720x 720 it worked
When you upload your solidworks model then wait for the bar indicating the completion of your upload. After this click on select file hyper linked below the "Drag files and folder here". Then select your rendered image file for upload select one at time for safety, in case of slower internet connection. after that select other rendered file by the previous method. Then you will see Ready to upload button highlighted and its all done.