These are sketches of mechs that I got with Flans Mod along with some of their upgrades.
The three robots are the Proto Titan, Alpha Titan, and Zero Titan. The Proto and Alpha Titans are simple box shaped robots with the Alpha being bigger, but the Zero is a much larger, more impressive looking robot. All 3 can be customized with a wide variety of tools and accessories, making them, multi-purpose robots. They can have drills and shovels for mining and rocket packs for flying. They can even be given the guns from the Modern Weapons Pack, but they must have the weapon's corresponding ammo placed in their inventory to use them.
You can also see DanTDM's review of this mod to learn more about the robots.
Mechs - Flan/Minecraft
Minecraft - Notch Mojang