They can in the next build .
Awesome. I suppose I'll wait to release until after the next build
Is the background color togglable? Wouldn't see much of black particles on black background
Yes, the background (and the grid, separately) will have RGBA sliders as well, so you can test your particles on different kinds of backgrounds. And it'll be an open-source .cap anyway so you could always just load an image in there if you want.
It's not going to have every feature available for particle settings, obviously, because there are a bunch of things you can't change at runtime. For instance, the texture. There will only be a handful of common textures to choose from (gradient ball, flame, sparkle, star, maybe a few others). You also won't be able to test any other effects like Overlay or whatever unless you change the .cap itself. But it's mainly for changing the rate, size, cone and such anyway.