Spice up your plain old tees:
Don't get that carried away or you'll end up looking like a Christmas tree. If you have a bedazzling gun, you can go all pro on your tee. You can sparkle up the collar and the sleeves or choose an abstract design to imprint on your t-shirt. If you don't have the bedazzler, you can do the same thing with fabric glue and sequins.
You can find all sorts or ideas on YouTube. There are a couple of videos that will show how to add lace to your old tee. You'll need a pair of scissors, a marker, paper and some lace. Draw a design of your choice on the paper and cut it out. Place the paper on the back of your t-shirt and cut a hole in that shape. Now use some fabric glue to go over the outline of your design and fix the lace on it. Once it dries you can turn your t-shirt the other way around and it's ready to wear!
This seems to be doing some rounds on the social media circuit lately. Choose a plain t-shirt and some brightly printed cloth or vice versa. Take a piece of cardboard and cut it out in a pocket design. Use this to trace a pocket-shaped design on the cloth and cut it out in the same shape. Now sew this colorful pocket on the plain tee. Definitely this will add a pop of colour on your plain t-shirts.