What's the rules to post an image

I'm newbie here and after some post many ones have been deleted

I'd like to know the rules to post an illustration (image size, dimension, upscale/resize dimension and another...). I see nothing about in the forum or the help section.

Thx for the answer.
There are probably people who can give you a better answer but probably the #1 rule is that the minimum size of an upload must be 1.6 megapixels
Thx kawaiideath i see this in the sticky but nothing more about the request...

Must i believe there are no rules exept this one?
Thanks you very much :)