I think clothing is a very good route to take for Oddworld merchandise. It tends to have very flexible design prospects. And be cheap. Just gotta be careful with the way it's being done, it sort of becomes ironic in a terrible way if stuff's being produced in sweatshops by people being paid virtually nothing and all.
For some reason I really think the idea of a stitchlip bandana is fantastic.
Maybe something like this. Although come to think of it, this might be a better thing for Stranger merchandise... Still! It's an idea. A nice cosy idea considering the northern hemisphere is going towards the winter months now.