Forums → Support Forum → Photo Uploads

You can find the image URL by right clicking an image and selecting "Copy image URL", then paste it into where the URL should be

So the Google logo:

Just to prove a point, here's something off photobucket:

You need to use the direct link from photobucket. Everything else won't work properly.
Alternately, upload it on imageshack (use the direct link, if you have made an account there), or deviantArt (where you will need to right click-method).