Apply your texture to the box. Scale the box if needed. (A painting hanging on my wall
is 0.65 by 0.53 meters).
Make sure that you have only specified diffuse color for the box (set specular and
emissive color to 0 0 0, make the shininess 0.0).
Also, a better way to do things is to explode the box into faces (Edit Menu>Explode
into Faces) then go to the tree window and delete the 5 unneeded faces. Make the box the
proper dimensions BEFORE you explode it, this way you will not have to scale it later
(which may cause problems with some graphics cards). You will then have a single IFS
surface on which to put the image. It will be less work on the browser because the image
will not have to be drawn on those thin edges. (optimize, optimize, optimize; yes it
matters even on a small artwork when you consider it in the context of many items in the
total scene).
You can see where I deleted the unneeded IndexedFaceSets leaving just the one.
