One way would be to approach it as if you were writing a book in text format. A book with no images will describe things in a way that gives you a mental image.
Normally an author has a picture in their head and they convert it to written form. Except in this case, you are starting with an image (rendering) and then converting it to written form.
If there is a story behind the rendering, then include that, as it would make the description more compelling, both for people who can see & hear, and those who can't. People are more likely to feel a story than a technical description of the item.
Ideally, we get feedback from deaf and blind people. And perhaps some feedback from writers too.
I think we need to come up with a way to create a working group or interest group on accessibility, or get involved in an existing group. Because I think that simply asking for feedback from random people won't be enough.