Hey there, thanks for the contributions thus far. I just wanted to go over a few things for the sake of future editing...
For page layout, use the Winnowing Hall article for reference in regards to the ordering of sections. "Notes/Trivia" and "External Links" should always be at the end before the navbox, and make sure the visible line before the navbox remains. Also, the PSX and Saturn soundtracks are identical, so I've removed the latter.
Regarding the images, check out some of the gallery images for the heretic levels to get an idea of the recommended format. 4:3 is preferred, make sure the HUD is completely hidden, and try to have the enemy/enemies a lot closer to the player (the images will be small enough on the article already). Also, make sure they're labeled properly (your first few are just a string of numbers). The image you uploaded of the Slaughtaur is a little better, but still needs improvement. I'll give you some time to fix the images, but I'll be deleting them in time when I do another round of image cleanup on here.
I'd recommend you refrain from further image uploading until then, since these ones will be deleted anyway. You can resize/disable the HUD with the "+" and "-" keys, or in the options menu, as well as change the aspect ratio and other things. The enemies are still a bit too small and far away from the player, try getting a lot closer to them. If you're worried about damage, just enable god mod. Also, please remember to actually give your images a name instead of just random numbers.