Can a lone pair be involved in cis/trans isomerism? I was trying to find whether a molecule showed isomerism, and this is what I came up with. 

I thought this was the case as I took the nitrogen to be sp2 hybridised, thus trigonal planar (with the lone pair not shown on the diagram). The molecule can't rotate about any single bonds because resonance makes the whole molecule planar. Am I right in thinking this shows cis trans isomerism? If not, what sort of isomerism might it show?
Yes, due to the lack of rotation about the C=N bond this will display the desired isomerism. For a much simpler example see $ \ce{N2F2} $



(taken from https://en.wikipedia.org/wiki/Dinitrogen_difluoride )