After i use them as keys to open to doors in the dungeons, can i vendor them? or do they have more than 1 use?

Yeah, but I think they make good decoration and you might reuse them sometime maybe.

I sold the ebony claw for Kovanjund (Jagged Crown quest) to Belethor for a decent amount of money a long, long time ago, since I am pretty sure I won't be going there again. He's kept it in his inventory ever since.