Aside from moire, there's one more hurdle of scanning LP jackets you need to surmount--that pesky problem that album covers are just too big to fit on the scanner bed -- at least on anything but a professional grade scanner. Not only is the scanner bed not wide enough, but unless you have a legal size scanner, it isn't even long enough! Both the bottom and the edges of an LP will be cut off on the scan. Fortunately, there are workarounds.
Stitching the portions of the scan together
The easiest way is to scan the LP cover in sections, and then stitch them together in your photo editing program. Even though most scanner beds are not legal size, they are a bit bigger than 8.5 x 11. Mine measures 11.7 inches long. Still not large enough for an LP record jacket, but close enough. I simply scan the top portion of the jacket, then turn it 180 degrees and scan the bottom portion.
Photoshop and Photoshop Elements makes it easy
Recent versions of Photoshop and Photoshop Elements have a nifty Photomerge command that will automatically stitch the two halves together for you. with the two scanned halves of the LP jacket scanned and saved to disk, choose Photomerge Panorama from Photoshop's File menu. Choose the two scanned halves of your record jacket in the Open dialog and click the Auto Layout on the left-hand side. Click Okay and, in about 30 seconds, your two scans will be merged into one nearly seamless record jacket. Save the stitched image for adding to iTunes.
The final scan should look pretty good. Two of the corners may be cut off because the jacket didn't fit completely along the width of the scanner, but I find that I can usually place the jacket on the scanning bed so that a non-crucial element gets cut off on the final scan. Judicious use of the cropping tool in Photoshop can convert the final scan to a perfect square shape a la a real record jacket.
A good resolution at which to save the final jacket is 600 x 600 dpi, which is the size of jacket art work of the songs purchased from the iTunes store. Remember if you save the image at too high a resolution, it will bloat the size of your music file, as the cover artwork is stored as part of the music file itself. This will allow fewer songs to fit on your iPod. However, if you have iTunes or an iPod touch (or iPhone), with the album jackets present on all your songs, you can make nifty use of the Cover Flow view in browsing your music collection.
Now admire your work in iTunes
With the music digitized and the jacket art scanned and added to the music file, it your work is completed!
