itch.io

Use an art program, photoshop, Paint.net or whatever. Using the template, search for what you want online that will fit the template box. Search using a PNG file. Use your the selected image as a mask layer and over lay the location template. Make sure to remove the background on the mask layer. You can literally add anything.  A weapon, a bottle of alcohol, a laser pointer, a sexual aid...etc. just position the size and angle to fit the mask. Add color on a separate image calling it the color mask. You are only limited by your imagination. Once you create the image, insuring it fits the position template, create the new asset in game. Adjust the image as needed.

Create your own assets. I found it a little overwhelming at first, but has a quick learning curve. Creating breast sizes from A-cup to F/G cup, jewelry, even "transgender" models with appendages below the waist. You just need to play with how you want it to look and if you are not doing an animation, it is much easier. I purchased the main program and the Sci-Fi add-on just to get an idea of what to do. After that, it was about 4 hours of teaching myself and learning from my mistakes how to create custom assets for my game needs.