We do have size limitations, but they are global in nature and not category specific. However, because the code is already in place to check for these limits, it wouldn't be that difficult to modify the code to add in category specific minimium limitations.
We do allow for downloads of images in a ZIP file, but we do not count the number of downloads. The files contained in the download are the bigger images, but we don't limit people from clicking on a medium image to see the large one. That would also be a modification you would have to make.
Please do not PM me for support or sales questions. Thank you for your understanding.