Pop Art

This is a nice easy but effective way to learn about digital paint tools such as Photoshop. It requires the use of layers for best results and the bucket tool. Some excellent info plus a short video (under five minutes -- possibly good for a starter) about Pop Art presented by Alan Cumming can be found on the Tate Modern's website. 

Tate Modern Pop ArtDigital Pop ArtDigital Pop Art

Barcode Art

A lesson that uses Photoshop techniques to create a barcode and turn it into art. You will need the ID Automation or similar barcode font installed.

ID Automation Font

For inspiration, check out these Kawaii barcodes:

Kawaii barcodesPowerPoint

Take a look at this site for some information about Pop Art artists. Also, there are many great examples of Pop Art in fairly high resolution.