It's not easy to come by high-res scans of 'clean' artwork. When I made those scans (for the purposes of poster printing, which I never actually did) I tried to remove the IBM logos etc., but it was basically beyond my capabilities. The covered sections of the box art are hard to find in an uncovered form, and when they are there are usually problems - such as the image being black and white (like the Monkey Island manual) or the resolution simply being too low to feasibly blend on top of the original.
The easiest way to do this, short of someone turning up with clean images from somewhere, is for someone who is good with photoshop or PSP to just 'invent' a replacement for the logos. Paint it in, clone it... whatever.
But the short version is that I can't help you.