If you want to flash ROMs or random ZIP files to your device, you're more than likely going to use TWRP. This is the most widely supported custom recovery for Android, but it's been a while since it got a big update. The 3.0.0 release is just about ready, and it brings a ton of changes, not the least of which is a new theme that's more in keeping with Android's current look.
Here's the changelog posted by the TWRP team. It's not a complete list of all tweaks and fixes, but it covers the main points.
- Completely new theme - Much more modern and much nicer looking (by z31s1g)
- True Terminal Emulator - Includes arrow keys, tab and tab completion, etc. (by _that)
- Language translation - It won’t be perfect and especially some languages that require large font files like Chinese & Japanese won’t be availble on most devices. Also some languages may only be partially translated at this time. Feel free to submit more translations to OmniROM’s Gerrit. (mostly by Dees_Troy)
- Flashing of sparse images - On select devices you will be able to flash some parts of factory images via the TWRP GUI (by HashBang173)
- Adopted storage support for select devices - TWRP can now decrypt adopted storage partitions from Marshmallow
- Reworked graphics to bring us more up to date with AOSP - includes support for adf and drm graphics (by Dees_Troy)
- SuperSU prompt will no longer display if a Marshmallow ROM is installed
- Update exfat, exfat fuse, dosfstools (by mdmower)
- Update AOSP base to 6.0
- A huge laundry list of other minor fixes and tweaks
The new version does look much nicer than the old one, and the theme engine is smarter too. If the engine detects an incompatible theme, it defaults back to stock rather than just breaking. Speaking of things breaking, there are a lot of changes in this version of TWRP, so there might be some boot issues early on. It would be smart to keep an older version of TWRP handy in case you need to flash back.
You can track the progress of builds on the build queue. There's still some work before stable versions are live, but they're in process.