@tjwoosta - what you are asking for is something highly specific. As it will already take more than enough time to crop, edit, and match the rom to the game, you are already looking at a task that is going to be taking up a majority of your time. The whole "auto download all" topic, like sheep2001 has stated, has been brought up a million times over the existence of this site. If you want to pay a scraper yourself to achieve your end goal, you might want to do that. Only saying that because over the 5 and a half years that I have been a member here, the admins haven't budged on the topic ONCE. There has never been a good reason, and the cost to host such an option would be astronomical.
Not sure lately how often new covers are created now a days, but lets say you download all the pictures. A month later there are 150 more, but you are too lazy to re-download them manually, but your internet is extremely fast. Might as well download the entire site again. Ya.... No...
I understand changing the artwork on roms and such, as I was fixing cases for the collectorz app a couple years ago. But I can tell you, you are already in over your head. Thank God hyperspin downloads and does everything for me. Maybe I have gotten lazy =P
We have the most authentic box art, yes. But our work is done freely. The people who have contributed their work does not get paid. It's all because they enjoy what they do, and want to share to the community. I can tell you right now that resizing, cropping, and changing existing art are a PITA. I don't see how since you can only do one picture at a time, you would need a backlog of pictures anyways. There is no way to do more than one at a time, so you can easily download the next picture (even on dialup) way before you finish cropping, saving, and replacing.
My $0.02 on the topic. But saying "I want to download all for roms", that is a highly specific reason that I can tell you right now, the admins won't budge for

Highly entertaining to me.... looked at the old Gameboy Covers in Cassette cases thread, and read someone (hopefully jokingly) offering 7,000 NES coverart for sale.
http://www.thecoverproject.net/forums/index.php?topic=5827.msg175593#msg175593 Say what you want on how harsh these mods are, but
download all is not happening