Found out what was wrong! Some entries in "graphicsinfo.conf" pointed to a blank frame in image set "Boulderdash.pcx". Looks like the author didn't do a very sound job on that ...

I disabled all references to the blank frame and also changed some other references. The attached "graphicsinfo.conf.txt" has to be renamed to "graphicsinfo.conf" and copied into "\levels\Boulder_Dash_Dream\graphics".

Another note, BD2K3 level pack seems to work too. Graphics might have glitches but it surely looks interesting. And the author did a very thorough job with custom graphics. Wish there was something like this for classic graphics as well ...