At 17 if she's never had a foal, I wouldn't try her regardless of what her confo was. For me, due to her looooong back, I would not breed her. QH's and Paints have gotten a little too long in the back for long term soundness, and we need to be looking at breeding for shorter, sturdier backs.
All that said, from a color and "She's cute" standpoint, if I were going to breed her, I'd look for a short back, well coupled, great shoulder, cremello or perlino to breed her to. Reason for that, she's solid, so unless you breed her to someone with spots and get spots, you just have another breed stock paint. If you go dilute, you get a buckskin or palomino and can register with the color registry.