This probably isnt possible but:

Loads of people have really large custom emoticons which take ages to load and then get resized anyway.

If you turn off Custom emoticons in settings then it solves the problem except that sometimes the people give them weird shortcuts and you dont know what they are meant to represent.

It would be nice to have a plugin so that you could enable a specific one in a conversation to see what it looked like so you know if it had the shortcut of 2 it was meant to be a question mark/ lol/ gd or whatever!

gosh !! hehe what is that !!!!!!!!!!!!

you know i dont think this is usefull !!.
or if it's even possible

but  u know regarding the size , i dont know if there is a plugin that specify the size of accepted emoticons!!

and if there is not, then this will be a good suggestion, like dont accpet emoticons bigger than pixlesXpixlex

cheers