You can paint plastic easily. First, lightly scuff sand the surface so that the paint adhers better. Use a plastics primer, like primer used on models. Then simply paint. Best to use an airsprayer, and don't paint all at once. Paint a light dust coat, let it tack up for 15 min, then another coat, and repeat. That way you won't get runs. Use a clear coat to make it more durable. There are also all kinds of pickguards for sale. Plexiglass with the image underneath is a great idea.