Signage covers many areas; the first thing that comes to mind is shop signage, which can include very simple vinyl lettering and graphics, that tend to be displayed on glass.
Vinyl comes in a wide range of colours, although the colours aren't limitless so you may need to compromise sometimes. Along with vinyl cut lettering you can also print images onto the vinyl. This looks especially great when you have a large photograph printed on vinyl covering a large window.
Another common option is the light-box sign, these have hard acrylic sheets inserted on either side of an aluminum casing with fluorescent tubes inside. These are quite a cost effective option especially if you only need to replace the acrylic inserts.
After this there are endless options - large photographic images filling whole walls, 3D forms that jut out, metallic cut lettering, gold and silver finishes, neon lights (these are not really used as often as they used to as it's a more expensive process) plus heaps more. It's only limited by the space, imagination and budget.