Keep it small.
Although it may look nice, there is no need to have a m ive signature pic.
1.) It takes ages to scroll through the posts seeing the same pictures of people's personal stuff.
2.) And secondly, those members that still use slow connections, are sitting there for ages waiting for your sigs to load... Very dull I'm sure you can imagine!
So, let's keep the size of our signatures to a modest level.
Thank you!