Here is a page of (some of) my Jake designs! This is the exact page I submitted to my real-life client. Numbering the drawings helped them provide feedback, and providing them on a plain white background helps ensure that nothing is getting in the way of the character designs themselves.
I added a quick color pass in two stages:

1) Used a round brush on a new layer above the line art (layer set to 'multiply') and on this layer I did a base-color pass

2) Switched my brush to 'multiply' mode, and on the same layer, added a very quick shadow pass ('multiply' mode on the brush made my base colors get darker with each pass.) My goal was not to 'render' the drawings, but provide just a bit more 3D form, and a hint of what the designs may look like in color.