Technically speaking, a character in a simple 2d game is usually a model created from a simple geometric shape, like a circle or square, with an image over it to make it look like something (a texture).
A sprite is just a bitmap (or other image) with a set of screen coordonates that move, based on user input.
Sprites are most oftenly used as explosion fireballs, smoke effects, and stuff like that. We won't need much of that since the HGE particle effect generator is awesome.
We can implement graphics as soon as i am given graphics files and told what goes where
Sounds too, like weapon noise, footsteps, agonizing screams...