I made three, one for each day of the expo, but they don't work. I have seen other people with three icons in their signature, what am I doing wrong?

What are you pasting in? To make a three-icon banner it's the same process, you just pick more costumes then 'generate banner' and be sure to copy the entire code

There's two in your signature there, the first is complete and the second is missing a chunk from the end which is why it shows up as some text.