I've placed them as a layer in photoshop and then added a neon paint effect outline over the top.
My 2D character will be a 'neon cowgirl'...here's the completed neon outlines....
New layers added, each with a new neon effect to build up glow. Legs, arms, head, hat, torso etc all on individual layers.....
The beginnings of the costume design....including stylised hair which should be good for 3D modelling!
Gun holster and lasso next!