I've seen several awesome tutorials out there for spicing up a plain t-shirt... ruffles, flowers, ribbon, applique. This is my version:
This plain brown shirt had a nail polish stain on the front but I didn't want to throw it away. So I drew lines on using a washable crayola marker (yes, they work great for sewing projects and wash out like a charm!), then hand-sewed little sequins onto each line. It didn't take long at all. And I bet you can't tell where the nail polish was, can you?!