How do I use my own image for a Bitmap pattern transparency?

Hi All, 
I used to be able to use my own image for a Bitmap pattern transparency but in version 2019 I cannot figure out how. No matter what I do I either get bricks or the option to purchase more fills. I cannot find a way to use/add my own. 

I use this technique to create glass reflections. I use a black and white version of the refection image as the transparency pattern.