mind machines or light and sound machines provide flashing light at frequencies that are entertaining and can also entrain the brain to those frequencies.
I use the Sirius mind machine with blue light frames which are said to be more relaxing. The Sirius is a low end machine, but it gets the job done. There are a number of programmed sessions, I'm not sure I have explored them all on psychedelics, but one of the more interesting settings is the random setting (#23) which meanders through many frequencies. I prefer that one for the "trippiest" visuals, but at the same time I find it slightly arousing as it often goes into some very fast frequencies - way up into high beta. I often found myself using the slower frequency deep meditation setting (#11) instead, but it's not as visually interesting.
Most of the mind machines can play audiostrobe encoded files, which allow you to go outside the programmed sessions and play any number of commercially available sessions (generally combined with music), or design your own with software like NeuroProgrammer. I've been experimenting for a while and seem to be settling on a simple design that focuses on the range of alpha and theta, roughly 4-12 Hz, ramping up and down from roughly 4 to 12. I find less than 4 makes the visual field less continuous, and as I'm trying to keep things relaxing I keep the high end to 11 or 12. I've been tweaking the rate at which the frequencies ramp up and down so that the overall visual field is stable and comfortable, yet slowly changing to maintain interest. I play the short audiostrobe file on repeat into the Sirius using a cheap mp3 player (an old SanDisk Sansa Express that I attach with rubber bands to the Sirius). I have music playing separately.
I had always found the LEDs to be a wee bit focused in a small area over the eye (as one might well expect). I had read about the Ganzfeld effect (even experimenting with ping pong balls cut in half to get the effect), and the Laxman light and sound machine which diffuses the light over a broader area with amazing effects, and began experimenting with diffusing the light from the Sirius light frames.
I began to use material cut from a plastic milk carton, sanded down on both sides with fine sandpaper to increase the diffusion of light. I found this improved the experience for me quite a bit, providing kind of a gentler experience and diffusing the light stimulation over a much wider area. This does reduce the brightness a bit, and I ended up using some white paint around the LEDs to increase reflectivity and brightness. After about 4 prototypes I settled on the following design, and am quite pleased with the results.
Pretty simple actually. It attaches using the little tabs on either side, with the tiny screws that are part of the lightframes. You can see the bright white areas where the eyes would be - that is the white paint around the LEDs. This does not provide the Laxman type effects, but I like it quite a bit.