Environment:
Windows 10 Home v12041.508
Oracle Java v1.8.0_51
Minecraft v1.12.2
Twitch Launcher v7.5.7419.39417

Mods:
Forge v14.23.5.2854
CreativeCore v1.10.25
LittleTiles v1.5.0
OpenPictureFrame v1.4.40

With just these mods, I get an error at launch:

The game crashed whilst initializing game
Error: java.lang.NoClassDefFoundError: com/creativemd/opf/OPFrame$1
Exit Code: -1

If I uninstall LittleTiles or OpenPictureFrame, the game launches successfully.

Update OnlinePictureFrame.