When I search around the internet I see a lot of creative ideas for Art Journal covers. My personal all time favorite has been to use the readily available and AFFORDABLE canvas boards. I tend to use the 4"x6", and 5"x7" sizes...I find that size of a journal easy to work in and they fit easily into a bag or backpack so I can always have them with me.
The canvas boards make the art journal STURDY -- which is a huge plus to me because I tend to give it a lot of abuse And, of course they will readily accept a variety of mediums when it's time to design the cover. Punching holes in them is very easily done with an awl as well -- and I don't need to insert eyelets because of their sturdiness and ability to easily handle the waxed linen thread I stitch with.
So, my question to you is ....what do you use? Am I missing out on anything I should try? And what sizes do you tend to create your journals in?