I did these in a few minutes using the randomizer, but you do have the ability to select you own colors, background and fonts.
Some tips; You must have java loaded on the computer and have the firewall set to allow for java. There is more information in the FAQs. I have also found it very helpful to create the test in Word and copy and paste it into Wordle. This eliminates the frustration of loosing all your test if the Internet gets bumpy.