Well, I can't help in the banner department since I copy, paste and alter existing pics to make my signature pictures. As far as the spoiler tags go, we don't have that function here anymore however you may want to tell ppl in advance that you're writing a spoiler, leave plenty of space so that if someone clicks it, they won't be immediately spoiled. You may also want to use the color of the letters you're typing to match the background you're using here. Then all someone needs to do is click and drag their mouse over that part and highlight it so they can read the spoiler like I've done below:
This is how I would do a spoiler!!!
