Again, probably HyperPie but you'll still need to add the roms yourself. There may be some out there with the roms but it's not legal to distribute roms. HyperPie as is was a little too flashy for me. I follow the theory that less is more. I wanted a nice clean interface but with all the artwork and videos. I didn't need all the flashy sliding art and things moving around on the screen which is why I decided to build mine myself.
It would be good for you to learn a little about the system anyway so you can fix things when they go wrong (which will eventually happen). Probably the biggest issue is dealing with your arcade controls/gamepads. Retropie makes it pretty easy but everything is done through Emulation Station. if you're looking to use Attract-Mode on a Pi then you're going to have to fiddle with things to get controls working.
I didn't use the scraper at all when I did mine from scratch. I used bits and pieces and all the artwork from the HyperPie image - just copied the artwork across into the appropriate folders. I put the Pi on my network (cabled not WiFi because WiFi is too slow copying) and then connected to it from my Windows PC and copied it across using the built-in file sharing. Out of the box you have file share access to the roms folder and I believe all the config folders.
Also I was building mine for an arcade cabinet. Are you doing a cabinet build or planning on using this as a console style that you hook to a TV or what is your plan?
Rich
EDIT: Another image you would want to check out is Floob's image. Find it here:
http://forum.attractmode.org/index.php?topic=705.0That one is already set up with Attract Mode but again you need to add the roms.
