You probably didn't converted it into a plugin correctly. Here, a guide about how to do this. Or you can just paste it into a script section above main.
Nice tutorial! I use Greenshot to upload images very quickly. Besides a way to capture screens/print screens, it allow to right click in an image file and select to upload to imgur, with the link copied to your Ctrl+V.
You can even set imgur as default behaviour.
Games Corner
I like the thread thumb, but please make the dimensions/aspect ratios clear to the developer. I need to do try-and-miss to understand the parts that were cropped. Also an option to override the thumb (with a external image link) would be nice. Currently, I need to put the thumb...
This isn't directed related with this script. but with MKXP-Z and/or plugin manager.
An idea: If you use it as plugin, try to open the text file and save with UTF-8 encoding.