Quote - ** I just don't see how a tasteful nude thumbnail is not allowed.**

Please try and define the word "tasteful" so that it encompasses each person's individual level of tolerance and opinion.

It's not possible because what is tasteful to you may  not be to me and vice versa.

I'm sure there are many that would consider a close up shot of a giant nipple on a size 99XXX boob  "tasteful", and then there are those that don't.

You cannot have a rule in place that is loosely open to interpretation so Renderosity went with an  "all or nothing" one.  In fact they took the word "Tasteful" out of the thumbnail policy guidelines because after great discussion it was determined that  there is no clear cut definition for it and it's too subjective a term to use because of that.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi