Not knowing what it is I can't really say.  The key is deciding what most people will consider in good taste.  I would suggest it would OK as long as it wasn't ...  not sure what word to use ... obtrusive?  flagrant?  too "in your face"?  I get rather irritated by the signature lines that go on for half a page or include photographs way too big for a signature.   But if it is something small and brief it will probably be OK.

I mentioned "in good taste".  That is an opinion.  The problem is a lot of people either  don't consider other people's opinions, or else for some reason they delight in doing something that offends others.  I've tolerated a lot of things that I didn't think were in good taste (not just on here but in life) but I also have told folks when I thought they were over the line.