[Edited: found a bug in sample code]

Ok, I have my mp and my characters all lined up so far, but how do I mae it so I can make my icons bigger?

The short answer is: each icon can be 32x32 pixels at most. However, with some clever programming you could make it appear that icons are larger--for example, create a mob with an obj attached to it, so they move together and effectively create the illusion of a 32x64 icon.

Here's a link to a discussion that has more information:
Big icons...

Hmm... just for fun, here's some code that might do the trick. It's untested, though!

mob
//The mob shows legs and waist; the "head" object shows torso and head.
var/obj/head/head
var/headType

New()
. = ..()
if(headType)
head = new headType(get_step(src, NORTH))

Move()
. = ..()
if(. && head)
if(!head.Move(get_step(src, NORTH), dir)) head.loc = null

human
icon = 'humanBottom.dmi'
headType = /obj/head/human_head

obj/head
layer = MOB_LAYER + 0.1
density = 0

human_head
icon = 'humanTop.dmi'