One geometric interpretation of (at least one term of) the potential function I've come across is as the Riemann-approximated area under an individual player's cost as a function of the number of players...
However, the potential function is not actually a function of the number of player, but of their strategies. Is there a geometric interpretation of the potential function for, i.e., a game with two players as a three-dimensional surface, where the input dimensions are the strategies of the two players or something like that, and the potential function's extrema (which correspond to Nash Equilibria) can be seen? Presumably, a game without a potential function would correspond to a surface without extrema?