With a bit of script editing, changes to the skybox, and a post effect, I managed to make Claustrophobia during daytime. I personally think it looks amazing
Thank you! :D
Someone here posted a MEGA link to the extracted version of the original SMS maps. This extracted version gives us access to all the files, meaning we can mod the game to our liking.
Find the image you'd like to use*, in my case the daytime skybox from Slender: The Eight Pages, and under Files\skybank\DTISkies\MOO replace each image with each direction respectively. U = Up, D = Down, L = Left, R = Right, B = Back, F = Front
*: It is suggested that you use something that's already intended to be a skybox, otherwise it might be difficult to make it look right
For the post effect, I went into Files\scriptbank\Claustrophobia\start.fpi and on line 28, located "setposteffect=" and set it to bloom. (setposteffect=bloom)
Now open the game and your changes should take effect.
This works for any map, although the 'skybank' subfolders differ from map to map.