From the Site:

CSS galleries can be a great source of inspiration, but if
you’re looking for something in particular they can be a bit of a
nightmare. They can also be a little repetitive, you’ll often
find the same design repeated on many of the galleries.
Since niche galleries have a tighter focus it allows them to be more
detailed when adding sites to the gallery, and although they
don’t update as often the quality usually makes up for it. Given
their focus the same design is a lot less likely to be featured on more
than one of the niche galleries.
This is not to say the general galleries are going away, they
provide a steady steam of inspiration, but when you’re looking
for something in particular niche is nicer.
Below you’ll find a list of niche galleries, that focus on
things from color schemes, to layout, and specific content types.

See the List