I have been a fan of "long" stones for a really long time, and the beaches around here seems to have quite a few of them.
Perhaps their relative "rarity" is part of what appeals to me.
A "long" stone presents a completely different design challenge from a round stone. Whereas it is certainly possible to create some "version" of a round symmetrical "mandala" style design, long rocks lend themselves better to what I call a "garland" or "vine" type design.
What I mean by that is that I like to use the curves and shape of the stone and "wrap" the design around it. Sometimes the stone will have a soft curve, a bit like a banana, and I try to work with these subtle natural shapes. The core idea behind an Alchemy Stone is to always try to make the decoration and stone seem like they "naturally belong" together.