StepMania has had a long history with lots of super cool themes. But as the software has evolved, a lot of older themes are no longer compatible with modern versions of StepMania.
These are themes that work with most modern forks of StepMania (like OutFox, ITGmania, and Stepmania 5.1b2).
Simply Love boasts a distinctly simple aesthetic, competitive-tier visual clarity, and quality-of-life features. It is unquestionably the most popular ITG theme, due to its competitive nature, consistent updates, and customization.
It is included as a default theme in many different ITG simulators, such as NotITG, Club Fantastic, and ITGmania. It has so many bundled features, that many other modern themes are based off of Simply Love. Needless to say, it is highly recommended as a starting point.
Horsey's fork of Simply Love is a fork that aims to only add to the existing Simply Love theme. No features from the mainline theme are removed. But this fork adds a several notable features such as: re-designed ScreenSelectMusic with more player statistics, a clock on home mode, and re-addition of score vocalization.
Sereni's Vertical Simply Love is a fork that adapts the Simply Love theme for use on single player setups with vertical displays.
Main feature of the fork is visually bigger arrow scrolling space. However, you sacrifice Edit mode, Casual mode and some other features.
Waterfall is a theme developed by SteveReen, originally based off Simply Love, which has a number of new features mostly focused around improving timing/accuracy. Originally developed for ECFA 2021, Waterfall features new "default" timing windows that are stricter than either ITG or DDR (though the "legacy" ITG timing windows are still tracked and shown on the song results screen) and multiple life bars that function similarly to the life bars in the rhythm game "Sound Voltex."
Waterfall Expanded by Zarzob adds more QoL and fun features to Waterfall. Waterfall Expanded last update July 2022.
Digital Dance is an ongoing Stepmania 5 theme that was originally forked from Simply Love, but is now it's own entity. It's being made by JNero with numerous QoL improvements and streamlining changes.
It includes features such as a custom lua song/course wheel, song search, better sort/sub sort options, song filters, greater depth and control over on-screen information in gameplay (such as Groovestats song records, step statistics in 2-Player mode, and column cues for steps after a player determined break), mouse controls, and many other bonuses. It is compatible with both ECS/SRPG events and ITL, as of the most recent versions of those events.
In The Groove 3 Encore is a revival of the classic fan-made In The Groove 3 theme for Project OutFox.
Although originally a straight port, the theme has come a long way, and now contains many of the quality-of-life features of modern ITG.
In The Groove 2 SM5 is a direct port of the In The Groove 2 arcade theme to StepMania 5.
These are themes that work with older forks of StepMania (like OpenITG, StepMania 3.95, and original ITG).
Simply ITG is a theme for OpenITG and NotITG that attempts to backport modern Simply Love features into the original arcade ITG2 theme.
This theme is great for those that enjoy the quality-of-life tweaks that Simply Love features, but that prefer the aesthetic style of the original arcade game.