Does anyone know what the three other extra PSP themes are on the NA website for BBS? I think that that they are Ven, Aqua, Terra themes, but it's just a gander. Any other ideas?

Yea probably or maybe a xanehort and terra theme, and ven and vanitas theme, and and aqua and mickey or aqua theme as three diferent themes, or these three:

Xanehort and Vanitas

Aqua, terra, and ven (as one theme)

and for the final theme, little sora and little riku or mickey and little kairi.

Well, iirc, the Japanese SE members also had a theme for Terra, Aqua, and Ven each. So there's probably that, and maybe a theme with all three of them altogether like on the JP site.