BFD 1.5 offers a number of ways to create your own unique kit sounds. Here's a layering technique that works well with both the stock BFD sounds and the 8 Bit Kit.

Kick Layering

Click the picture of the drum kit to go in to Kit Piece Inspector view. Now load a regular kick in to the Kick 1 slot, and a floor tom or an 8 Bit Kit 808 kick in to Kick 2 (to load a floor tom in to the kick slot, use the "Type" pull-down at the top of the Kit Piece Browser). In the inspector for Kick 1, click "Link to kit piece" and chose "Kick 2". Now triggering Kick 1 will trigger both kicks.

To use only the attack of the acoustic kick, turn up Env Damping to 75% and Freq Damping to 50%. Then tune the floor tom in Kick 2 down by 30% or so (until it blends nicely as part of the kick sound), and adjust its Env Damping so that the sustain isn't too long. Finally, adjust the direct and ambient trim levels to taste.

Snare Layering

You can do the same thing with snares. Layer two snares, or use a Mid or Hi Tom or one of the Frame Drums or Hand Drums in 8 Bit Kit for a second source. Try tuning a low snare up very high, turning its Direct Trim to zero (so it's just providing some buzz in the ambient mics), and using a Frame Drum to provide the body of the sound. Or, you can adjust the envelope time of a snare to give a short, "crack" attack, and then use the body of the frame drum.