Been making a few warp portal markers for my Urban War Koralon (although there is nothing stopping me from using them for other games). U.W. provide counters to represent the portals, but as they are small and sit flat on the table surface they've never seemed to represent the technology that is described in the rulebook. If my scary aliens are to charge through space I want them them to do it through a swirly magic door!
GIMP) to size and shape it into the desired doorway shape. Somewhere in the Urban War forums there is a thread mentioning that portals should be 40mm wide, so that is roughly the size of the base.
The picture was then mirrored in GIMP, printed and cut out and folded to make it double sided (the mirroring in GIMP keeps the swirls going in the same direction)
The final part was laminating to give it a bit of durability and rigidity before slotting into a stand base (I bought these from EM4 Miniatures).