Yeahhhhh, got my computer to work!
Now this is my result:
Everything works perfectly! Thanks ^^
EDIT: If someone else has problems with this:
1. Copy the classes GuiWorldSelection, GuiListWorldSelection and GuiListWorldSelectionEntry to your mod and edit the drawEntry method in the GuiListWorldSelectionEntry class
2. Create an class that does this:
(you could also use the InitGuiEvent like I, depends on what you want to do! When the events are called is really self-explanatory)
And register the event in your client proxy or client side in your main mod or common proxy init method!
3. Here's the source for the event class:
http://pastebin.com/w1E98q97
Don't know if there's an easier way but I hope it helps ^^