Here's a couple of PNGs.
The first one is your original image scaled to 80 square pixels as required for an avatar. The file size is 9k.
Since the image is being scaled to 6%, I thought the outline work looked a little weak so I added a 12 pixel stroke (to the original) in the second version. This one is only 9k too.
Since these are PNGs, there is no loss in quality like you will get with JPG.
I think the character looks great but since the forum's icon size is pretty tiny, it might be better to draw it a little simpler and with thicker lines overall.
Oh, also I framed it inside a square canvas to fit the forum's 'avatar' format.
Hope this helps.