Okay, I was able to trace down the error in your code. So, just fyi when I first imported this latest version there were alot of = new() initializers for dictionaries/etc that had to be corrected to their proper formats (i.e. = new Dictionary<string, string>().
As for the source of the problem, it is in Player.cs Line 255 the FillPlayerTexture method. In your tutorial you state the path to use for the sprites should contain an ending slash, however, in the code you add that slash for the user already. So if they follow the picture in your guide, the path will wind up with a double slash (//) and not find the texture. And since there is no error handling for that scenario (no else statement in the method), the user is left with no rhyme or reason as to what's happening. So the resolution was simple, removing the ending slash in the sprite path and the textures came right up. Haven't tested it beyond that but anyways, hope this helps. Damn good asset though, very good job!