Wow, thats impressive. Had you thought of using it as the backplane for a small TFT panel? Thats how my 12ft projection TV worked, using overhead projector hardware. The picture was easily as bright as that, and you can throw the original cartoon R&M portal on the wall with it. ;-)
I dont know how hard it would be to strip down a small TFT though, mine was 12" to fit an A4 sized Fresnel.

I was trying to keep the most expensive thing in this build to be the Arduino that drives it, hence the jumping through hoops to use static images.

Ah, well that makes more sense. I was just thinking, projecting the original portal doesnt get any more 'real' is all. That is a sweet mechanism you have either way...

I'm making the lens diameter and focal length just variables you can tweak in the model, if you have three of these lenses.  The cheap ones I got are 23mm.  The body model as it stood was only 30mm tall though.  I'll change it to 35mm.

I have two 30mm lenses, but I have three 18mm lenses, they will work fine, the image dia. will be smaller but distance will not be affected much.

The 18mm lenses should pretty much exactly match the "real thing". Just give me the focal length, or about in a day you can download the source and do it yourself.