The loading time is an intentional change. Basically, I noticed that there was an issue with cached files - when old files get deleted new ones can overwrite them, the problem is that if the browser caches the file then it will load the old one instead, which can cause different computers to use different images for things. This is a bad thing, so I removed caching in general. The problem is that if a room is loaded before all the images are then stuff can happen without you being able to see it, which is also a bad thing. So rooms take a few seconds to load now (but only once per session; files are still cached within a session.) The game does not wait for sound files to load though, which is why sometimes music loading is off. This issue can be mitigated somewhat during gameplay by using the "preload room" event a bit of time before entering the room, but the world builder still has to wait. (I might add a function to automatically preload rooms if there is a gate leading to that room in the current room.)
As for the game itself running slowly, I'll have to check - it's possible that something in the code changed to be less efficient than before. My computer is pretty fast, so I don't see all of the issues, but I'd like to keep BW running at a solid 60 frames for even mediocre computers. I wonder if there's a way to simulate a slower computer using a faster one?
I uploaded a bunch of interior tiles recently, and tagged them with "indoor". Not sure if they go perfectly with Hyptosis, but you can check them out. If it's a color issue, you can try recoloring the tilesets (making the color black or white and adding a small amount of opacity can make the colors less "bright").