I made some shields for some of the orcs in this post:
a-mess-of-orcs. Since I didn't have any spare shields that fit them the way I wanted I ended up making some shields out of plastic card and a bit of sculpting putty (the latter mostly to sculpt straps like the one you can see on the orc with raised shield on the left of the picture). I wanted the shields to look suitably scrappy, rough, but big and sturdy. Looking at the photo, I may want to "dirty" them up a bit. I think they look a little too clean and shiny.
(click to embiggen)
These guys are orcs of the Black Eye. I also have orcs of the Red Eye, the Bone Head orcs (skull and sometimes bones as their emblem), and the Broken Bone goblins, among others.