Is it possible to DYI a Double-sided/Dual Image Screen

Any translucent fabric will work, the image wont be as bright as black out cloth since some light will be going through. You will also have to worry about people being able to see into the projector lense from the 2nd side (if they are close to to the centerline axis). Also note the second side image will be mirrored. Dazian fabrics had a sheer / translucent type fabric that should work.

material designed for that sort of thing exist via a company that specializes in Stage and Business displays. It's not cheap. Other "DIY" things work "pretty good" but almost all those "others" have significant loss of brightness on one side, and most all of those have a degraded image on the "projected side".

It's "not" having that degradation that make the Mfg. material cost a bundle.

Stretched Spandex is most likely your best, "least expensive" option followed by a specialty Rear Projection Back Drop material from Diazan

Welcome to AVS.

Here is a thread related to spandex screens http://www.avsforum.com/avs-vb/showthread.php?t=1228287

Can tell you first hand experience that works great, specially for a one time use. However, ambient light, like with any projector, is a factor on the side that the image is being projected onto. If you use the screen for a rear projection, if you limit or have no light on the rear side, you could have ambient light on the front side and the image would still be acceptable, this is one of the advantages of rear projection.

Now if you want to see the image on both sides ambient light comes into play plus the consideration mentioned above.

If you consider a spandex screen, the more cotton the fabric has the better, also there are 4 way stretch and 2 way stretch fabrics.