If you are looking to add a bit more dimension to your 2D style characters in After Effects, have a look at this preset from David Gruwier. Dynamic soft shadows preset adds a slight simulated shadow to anything on which it is applied.
Initially developed (but ultimately scrapped) for an animated series David was working on, a single click can dramatically change the look of a character. Admittedly, David mentions that the preset was never a fully polished tool: “This also means that the animation preset has some bugs that I never fixed. For example, the script doesn’t work if the XY controller is exactly in the center, so move it before you apply it. This is not meant as a fully fleshed out tool, but just as a reference or starting point if anybody is interested.”
Still, the Soft Shadows preset works fine, and is an easy way to add a bit more dimension to animated characters. Download the Soft Shadows preset here.