We use ab initio density functional calculations to investigate the structural stability and vibrational spectra of small boron aggregates in different charge states. In search of candidates for the largest stable 2D boron aggregates, we focus on systems with one atom less than B-20 clusters with confirmed 3D geometry. Whereas the most stable structural isomer of B-19(-) is two-dimensional, in agreement with experimental results of Huang et al. [Nat. Chem. 2, 202 (2010)], the second most stable anionic and the most stable neutral and cationic species form a 3D pyramidal structure that had been missed previously.