Optional options, auto resize, specific categories

Would be great to have optional fields so that it isn't compulsary to upload a thumbnail.
Better though is to automaticly resize and thumbnail the uploaded picture.

What i really miss is the option to let users upload their products in specific categories only.
In my example my users have second hand files which i only want to be in a specific categorie "2nd hand".
The new files (by me) has to be in another categorie directly in the VM shop.
Thnx!

Jasper