This one... Actually isn't that bad. The shine came out okay. It's not great, but it does the job. I need to find a way to soften out corners without aliasing. The shading at the top is okay, but the shading at the bottom... Well, first of all, it was only the one colour, then (at someone's suggestion) I added another one, and that improved it. Also, earlier the colour was too dark, and changing the colour made the shape seem a lot more reasonable. So that's nice. Still not satisfied that it looks like a blob though, rather than a stamp... Oh well, hopefully I get better soon.
Also, interesting fact, that image is half the filesize of this text explaining the image.