I put this question before when I ask about avatar in mini-profile. I ask then what code must I put if I want a 350x350 px avatar on my forum. Someone advice me that to put in my global footer this code:
/* Allow 350px by 350px remotely hosted Avatars in Mini-profile */
This code is better suited for the global header than the global footer so that it can declare those style rules before the actual elements affected by them are rendered on the page.
If you're feeling especially pedantic all of the stuff between <style> and </style> belong in the style sheet of the theme(s) you're making this change on so that it only affects that theme and not every theme installed on your forum. This doesn't really matter with the number of themes you have right now, but if you ever plan to install a theme authored by someone else you may want to keep this in mind as your global header/footer codes run on all themes and may have an adverse effect on themes set up to display their mini-profiles and avatars a certain way.