So, I've been doing a lot on the forums lately, and I noticed that almost everyone has images of their character in their signature. i, being a general newb at all things Starbound RP, don't know how to do this myself. I wouldn't post this thread if I could find a tutorial, buuuuut I can't. So yeah.
I'm pretty sure all those people do is take a screenshot of their character, then crop it and use it as their signature. I could be wrong, but that's how I would go about it if I were you (unless there's a simpler method I don't know about).
Photoshop erases weirdly, and MSpaint leaves white behind. Is there a program I should use, like GIMP or something?
I personally use GIMP, and I do recommend it, but Photoshop should work. You may need to add an Alpha layer when you erase the background, otherwise you'll probably end up with that white background instead.
Photoshop, create a layer to erase the white background, then save as a .png or (ideally) a .tiff to use it as a signature. Need help? Send it to me and I can do it for you.
Also, using SBSE, you can export a character as a png file. Its pretty helpful. Its one of the of the buttons in the main menu.