The central idempototents of a finite dimensional algebra form a finite Boolean algebra with 1 as the max and the central primitive idempotents as the atoms. They are The decomposition of 1 into central idempotents is thus unique. So the central idempotents are the face lattice of a simplex. The order is $e\leq f$ if $e\in fA$. Your simplicial complex would be the order complex of this Boolean algebra and so would be the barycentric subdivision of a simplex.
Added details. The boolean algebra operations are given by $e\wedge f=ef$, $e\vee f=e+f-ef$ and $\neg e=1-e$. The finiteness follows, for example, because one can look at the regular representation of the algebra $A$ by matrices and observe that the central idempotents form a commutative semigroup of idempotent matrices. Such a semigroup is simultaneously diagonalizable and there are only $2^n$ diagonal idempotent $n\times n$ matrices.
