Where could I find a picture of an old record album cover?

You probably won't find one for that particular song, unless you use a copy of a compilation album with Jolson on it that has the song included. Originally called "Waves of the Danube" it gained popularity when Jolson and Saul Chaplin published it under the name "The Anniversary Song. It was released by Decca Records as a single under the old catalog numbering system (#23714 B - the A side was Avalon).

Even though album cover art started in 1938, it wasn't in widespread, regular use by all the major record companies until the late '40's.

There is a picture on eBay of the record itself, though it needs some Photoshop work if you want to use it:

www.ebay.com/itm/Vintage-Avalon-Anniversary-Song-Al-Jolson-78-Vinyl-Record-4926-/350502146775

Here's a list of all the albums that track has been featured on....

http://www.discogs.com/search?q=al+jolson+annivers...

Just click on the right one and you'll be able to enlarge the cover art and presumably save it.