Did you know you can type in your own letters in a variety of fonts to use as a logo for your HeroMachine character? After picking the body style you want, choose the "Insignia" component, then the "Text" genre of items. By default they all say "ABC", but if you click on the actual item on the character, your cursor turns into a text-selection i-beam. Delete the default ABC and type in whatever you like, from numbers to letters.
On the UGO HeroMachine forums, for example, "monkeykid12" has chosen a text font from the "Expansion1" genre and created "High Five", who probably won't be a guest on an anti-drug "After School Special" any time soon, but who does look pretty neat:
It helps to choose a non-white color for the Insignia before selecting the font item to make it easier to see. Now get out there and make some heroes!