Here's what's been added in version 1.8:
Added the NPC Maker tools from EBF3, EBF4 and EBF5 to the Prototypes section
(more dress-up games, essentially)
Added the EBF5 Battle Demo to the Prototypes section
(this has a LOT of content, including every skill and non-boss enemy from the original version of EBF5)
Added 6 Steam trading cards and other community items
(these are still awaiting approval, but should be live in a couple of days)
Added a "Wallpapers" folder to the installation folder, with 7 wallpapers based on the trading cards
Added a check on startup for a corrupted Options.meow file, which fixes some rare problems
What I plan to do soon:
Optimize performance in Bullet Heaven and Adventure Story
Fix a few more minor bugs in various games