I used to own that Impurity poster,, it brings back memories, thanks:-)
I purchased a framed No Rest poster earlier in the year, it was kind of an admittance that I was unlikely to ever fit into my leather jacket again which had the face from the album painted on the back.. I think I told my wife that if I bought the poster and could put it up on the wall I would sell the jacket but unless I am offered silly money for the jacket it is going nowhere!
As for selling your posters, I suspect they will be like my leather, worth far more to you in sentimental value than anyone would pay for them.
N.