Hiya!

I started to give a long introduction about myself, but really, who has the time? LOL  I wanna continue with your awesome vTuber Kit,  so I'll get right to the point.  I'm seeing quite a few talented people adding hair, extra eyes, different clothing, Cosplaying, etc.
Where are they getting these things?  I'm old, so you have to be sort of specific with me.
Thanks in advance! ♥

Is there no help with my question or has support for vTuber Kit stopped?

Support has not stopped, and I know how to do this.

First, Get your image you want to import, I chose this image of the logo of the C programming language.

Second, open VTuber Kit and navigate to the star icon in the very top right corner.

Third, use the "+" to add your image and change the texture by clicking on the icon of the texture.

Forth, select the file from your file browser for your image.

Button overview:

<-> flips the item on horizontal axis

 the button with four arrows pointing inwards moves the object to your mouse cursor

the "RP" button pins the object to a certain part of the model

the button that looks like a grid clones the item perfectly down to the parameters

Sorry for not responding. I've been very busy with other projects and don't regularly check this forum. It's meant to be used for support, yes, but also for other users to help with questions too. 

Sorry for the lack of documentation. But looks like you figured out the custom item system! Yep! People with very customized models are either drawing the art themselves or commissioning stuff! Hope that helps you!