One of our volunteer peeps at DC Booth Fish Hatchery in Spearfish, had on a fun t-shirt one day that she had done herself! It takes maybe 10 minutes and adds a fun look to a t-shirt you may be getting tired of. I don't know why you couldn't do it with some other fabrics as well.
First, cut the sleeve hems off and cut them in half.
Next, at the top of the sleeve, cut 2 inches each way from the shoulder seam. Gather the top and tie with one half of the hem piece. Gather the bottom and tie with the other half of the hem. Wah La!!
Julie also added about a 2 inch fringe to the bottom of her tee. She's skinny so that looked cute.
The above is my hankie shirt and I also did the Julie Sleeves on it.