hi,
Yes you can create your own custom fill and it will appear as you like. I have created many of them.
First, create your desire fill image by drawing (lines/color/whatever...) it normally in ArchiCAD. You'll need to play with it a while to get the scale you like.
Then copy and paste into the Custom fill dialog (or something called like that....I dont remember precisely rightnow)
And play with scale/zoom setting in that dialog....
For the reason it turned black, please check the type of fill you are creating: solid fill or symbol fill or... ????
At worst, search for help in ArchiCAD 13
Cheers