Exactly as the title says. Stupid question
ACP > Configurations > User Registration and Profile Options > Length limit in Signatures
Isn't that for setting the max number of characters in a sig?
What do you mean by "dimension"?
There is a paid plugin at MyBB Central.
I tried writting my own, but I messed up my local server that I don't know if I jus failed or what. Will try later anyways.