Texture bitmap size

[dan_inv09]

I was trying to make a transparent bitmap and it wasn't lining up so good, so I was going to kind of serialize my attempts. At the end of the next one I put a number "...40&.bmp". Well, that really messed it up, no matter what I did to my bitmap it still looked like it was only using the upper left corner. Then I tried changing the number.

Is this a documented feature?

Does it only work with the "&"?

I can't find anyplace where it says don't put numbers (at the end?/with the &/etc.) or it will mess up your texture. Was this in the old help files? Should it say something in the wiki (or is that just a lost cause)?