Importing custom logo into game for new team?

I've made a new team, and made a rubbish logo for them quickly on photoshop, I've put it in the graphics folder and named it the teams unique ID which is how I thought it was done, but it didn't work.

Any Help?

Read this guide.

"404 not found"

Is the picture 180x180 and a .png?

It is 140x140 ... but so is all the other logos I use and they all work.

It is indeed png