As a character artist I divide my heroes and inspirations a few ways.
From a structural perspective I adore the work of Disney. Especially the grand masters such as Fred Moore and Milt Kahl. Those guys I have studied in some detail but of course any of the "nine old men's" work is worthy of closer inspection. I just love the way that their characters have a solidity to them. A real sense of weight and presence.
Moving on to the actual presentation of such characters I look more to the work of some renowned cartoonists.
In particular Bill Watterson (http://en.wikipedia.org/wiki/Bill_Watterson) and the Belgian artist Janry. (http://www.lambiek.net/artists/j/janry.htm)
Both those artists have a wonderful style to their inking. A kind of thick and very dark ink stroke that tapers beautifully. The thicker lines help to depict strength. Watterson uses these strokes in environmental elements such as trees and rocks. His Spaceman Spiff adventures often show Calvin as Spiff confronting an enormous space monster. The monster is generally quite jelly-like and the lines that depict it are varied and perfect for adding interest to the finished illustration.
I strive for this same impact in my work. I want the lines in the drawing to be interesting. For me a line with little or no variation if size or weight is pretty dull.
I also like the line to look like ink. I cannot deal with the vector style often found in contemporary picture books. It's far too clean and round and just a bit dull.
In my own work I opt for the Round Tip Pen in Painter X3. I modify it to have a slightly firmer grain.
I find that this gives me something like the same ink style as the artists that I mentioned above.
Flat colour is for me a little dull. Much better to see some texture. Watercolour is great for this. But so is a thicker oil with pastel or chalk.
Watterson uses a fairly flat colour style for his characters and reserves the watercolour for the environment. This is neat but not such an easy thing to pull off.
I'm enjoying the process of establishing a consistent style.