Not everything in steampunk is clockwork and old keys but they are important part of steampunk aesthetics.
All, those clockwork mechanisms are great and interesting for drawings, but if you don't know first thing about cogs and clockworks and everything looks the same you will end up with something so blah.

How to find different cogs to paint?
Google it! Google is a great thing to find reference and ideas but please, don't copy someone else's work, it is just rude.
It is not the point to draw the clockwork that can work, when you paint the point is for the painting to look good.
Sacrifice utility for better looking painting, always.
I will give you some great cogs i found online, for inspiration:




And a disassembled clockwork, this is super usefull


Old keys work well with clockworks and filigree, that is how they ended up such a big part of the whole steampunk thing. And they look so great on jewelry and accessories.
Image of an old key with filigree and maybe a small cog as an ornament is steampunk enough, don't overdo it, avoid your art being tacky.

Here are some more inspiration for you:




Have fun and good luck