I found this on weheartit but I'm assuming is from ImKittyRouge.
1. Fabric chalk
2. sharp fabric sheers
3. skull picture (google it)
4. slightly oversized tee. preferably cotton to hold the shapes of the skull better than something softer like an interlocking knit (jersey-knit).
1. find a picture of a skull or a simple version. narrowing google images down to clip art or line art will work great.
2. draw out the skull on the back of your shirt
3. carefully cut it out with the sheers
4. find something cute to wear under it!