It is indeed, it is comprehensive, detailed and absolutely brilliant.
Especially the Videoslots one.
As for themes most casinos tend to group by tabs similar to "20+ lines" "free games" "9-line slots" etc. Simmo is right I do recall one that had tabs like
"Adventure" "Fantasy" "Cartoon" but I too can't for the life of me remember it.
The casinos tend to list by lines/features etc. because it is the most popular amongst players - a player who enjoys say the 243-way game with 4 self-selected features because he has played Thunderstruck2 will be more attracted by TFROL/IR than say having a list with 'Norse Mythology' and finding Vikings Go Wild which may be a disappointment and is also unlikely to be available at the casino he/she is at unless a large multi-platform one.