Muslin is by far the best for acrylic murals - it is strong and thin which makes it somewhat easier to hang.

For oil murals you will need linnen (since oils "eat cotton") you can get thin "Belgum Linnen" in Pearl Paint.

summizing - you need thin material fore easier hanging.

here is also link to the Murals on Canvas Article:

http://www.truefresco.com/dcforum/DCForumID47/1.html