Those fonts you've employed are perfectly evocative and idiomatic of so many games for the PSX... Kindly excuse this stupid question: are the sprites raster graphics, and if so, can they be in any way compressed?

They are indeed! Specifically, they're BMP images I converted to an array of raw pixel data to store directly in the program. The PSX can draw 4,8, and 16 bit pixel data (with color palettes, or CLUTs (color look up table). Normally, you would store the images in TIM format which SONY created specifically for the playstation (I think). They are not, however, compressed and I don't think there's a way to.

This is so novel! Do you have any applications in mind? Moreover, which processes and functions do you test with an actual PSX and an emulator, respectively?

I'm thinking about making some sort of 3d car racing thing, nothing too serious though. Generally I test everything on an emulator (no$psx, which is known for being the most accurate) and only occasionally test on the hardware, just because it takes longer to load it on the playstation :)

Also in terms of 2D I think it might be fun to make flappy bird for the playstation