Help with making my mod

I'm going to make a mod (in the next few days you'll see a thread about it in Works-in-Progress), and I was wondering- could anyone help me make it?

A basic description of what will/should be in the mod:

-One new mode (what i need help with the most)
-Over 200 enemies planned
-At least 23 bosses, most being in the new mode
-10+ NPCs
-450+ weapons to be added
-27 ores
-60 armor sets
-4 biomes
-262 pickaxes, drills, axes, chainsaws, hamaxes, hammers, etc.

So, the roles required:

-Sprites...

Help with making my mod