For whatever it might be worth, I would recommend "A Symptom of Angry" ([link]). It uses vibrant colors, with stark contrast between warm and cool regions of the image. It also has a relatively low degree of highly-tiled complex regions; that sort of tiling look cool in certain works, e.g. [link], but might not have universal appeal. The contrast in "Symptom" between the disordered/crackled regions and the simple white curves, I think, should be something that appeals to everyone.
Relatedly, I have been thinking about generating print-resolution images from Apo, but the render times are fairly obscene (4 days for a 16"x16" 300dpi image [=4800x4800], oversampled at 2x). You seem to have some reasonably high resolution fractals. Have you found a way to mitigate this problem? Or do you just accept the large render time?