Make some ill robot shit - kitmash
Wow, fantastic concept design drawing! Details, man.
Looks like, start with Gundam kits. But it depends on what scale you intend to flesh these out to.
Most of the Star Wars models were various military model parts of various scales kitmashed.
But for the droids, there was mostly scratch building and thermal forming.
In your drawing, I'm seeing some Gundam, Ma.K., and electrical components parts in there somehow. I got boxes of extra DC electrical stuff.
There's also everyday stuff from consumer product containers that are normally thrown away.
Here's a couple links I have bookmarked of other people's work:
Maschinen Krieger Ma.K.
Jukabala Junkyard