I think if you do it from your PC though the change won't be reflected on your phone. Gmail applies two different signatures depending if you're accessing it from the web or from Android. For example I use ".:mobile:." on my phone, but this doesn't show when I email from my PC.
I have been trying to do it from my PC. No, I cant paste an image to the signature box. All it will take is text. That sucks because I need my sig and don't want to use Gmail without it. Of all the capabilities that Gmail has I can't believe it can't do that!
SGTiger, thanks for the response. I guess that's better than nothing at all. Not automatic so I can't do it from my Droid but at least with an extra step I can do it from my computer. That's further than I got the last time I tried to set up a signature with Gmail.