Hi Amy
You can create plaids in DIP in two ways
Firstly you can make your own by starting with a 1 inch by 1 inch square. Use either insert square and stretch and colour to make the lines at various widths or use the insert line. Create the pattern in the square as desired and then use the free filter from
www.redfieldsplugins.com to create the plaid background. There is a tut for using the filter in DIP in this thread somewhere ( try a search for tile)
You can also use the free trial filter called Plaid Lite
http://www.namesuppressed.com/design/
If you need a step by setp let me kno w
Ill write up a tutorial