2560x1440 resolution works, apparently, but not on my laptops. It has been added to the launcher options. Thanks to HBomberguy for testing it out and sending me the screenshot below (and also telling me to add it in the first place).
Also fixed a couple voodoo spells in NIGHTMARE and PANAMA thanks to zf13448's reports. Eyes of the Beast now works on Chupacabras, and Abyssal Gate now properly summons Arachno Demons. Also, added menu art to NIGHTMARE and BATTLES DLC main menus.
Lastly, I would like to request Steam friends to get these two numbers a bit closer together. Another 97 reviews would get me ball-moisteningly close to 500:
2560x1440 screenie:
EDIT: Reminder that there are 4 more days till the Flooded City Mod Contest deadline. No submissions yet, so claim that cash.
Complete list of changes:
SOURCE:
-Added 2560x1440 resolution option to launcher.
-Removed resolution checks in launcher (lots were marked unavailable but work fine).
SCRIPTS:
-Fixed using Abyssal Gate spell to summon an Arachno Demon.
-Eyes of the Beast spell can now be used to possess Chupacabras.
-(NIGHTMARE) Fixed Difficulty resetting to Wimpy in New Game+ in NIGHTMARE and PANAMA DLC.
-(NIGHTMARE) Fixed Steam achievements for beating NIGHTMARE.
RESOURCES:
-Added new main menu screenshots for NIGHTMARE and BATTLES DLC.
-New mask and scope screen overlays for 2560x1440 resolution.