If you want to create your own 3d object (like a skull that's a lock) you will need a 3d program also to create the mesh
Blender is free and good, if you have access to 3D Max, Maya or other programs they will work fine also.
What you need is this
1. GMT (Grimrock Modeling Toolkit)
viewtopic.php?f=14&t=3325&hilit=GMT
you use this program to open the LoG models files and export them out, you also use this to convert your own obj files to LoG format.
2. Blender or other 3d program to create your model
http://www.blender.org/
3. GIMP or other application that can safe out DDS formated textures.
http://www.gimp.org/
3a. If you have access to Photoshop the Nvidia Texture Tools come in handy
https://developer.nvidia.com/nvidia-tex ... -photoshop
Then you need to create your model, Texture it, Create a spec map and normal map for your texture. Define the material in your materials.lua, bring your object into GMT and safe it out as a .model
Define your object in your object.lua and then try it out in the game
I created a tutorial some time ago that goes into taking an existing object from LoG and changing it using Blender(took a pillar and made it broken). You can start by having a look at it
viewtopic.php?f=14&t=4043
I also more recently made a tutorial about how to create simple animated objects for LoG using Blender (spear trap)
viewtopic.php?f=14&t=6560&p=69317&hilit ... inn#p69317
If you run into any troubles then just ask again and we will try to steer you in the right direction
Skuggasveinn