I just saw that you are lacking some Hypostomus pictures in your DB.

Hypostomus micromaculatus, Gran Rio, Suriname

Hypostomus corantijni, Nickerie river, Suriname (H. nickeriensis being a synonym of H. corantijni)

Hypostomus plecostomus, Marshall creek (Suriname river drainage), Suriname
For the pictures in our DB for H. plecostomus it would be interesting to know where those came from, I'm quite sure that they are not all H. plecostomus, perhaps even none.

Hypostomus coppenamensis, Coppename river, Suriname
Cheers,