Frankly, I use low res packs even after using high-res ones almost entirely due to aesthetic reasons.
I'm gonna be real - Sphax 16x and Vanilla both look terrible; Sphax only works with higher resolutions due to its dedicated artistic direction calling for it, and vanilla understands nothing about visual design in terms of low resolution art.
There are certain texture packs at 16x which are simply a feast for the eyes, however. Packs such as Dandelion are fantabulous, with a cohesive visual direction and limited palette choice, they feel warm and vibrant. Packs with limited palettes and clear colour schemes, which focus more on colour, look great at a low resolution, often even better than things like LB. For all its grainy detail, LB cannot keep up with more artfully woven packs.
I can't give you much direction on your issue. Most of my post is a digression, but my point is that if you find a 16x pack with wide mod support and limited colour schemes, along with a focus on stark visual contrast, you'll likely find something near perfect right there.
If you don't mind putting in loads of work, you could even make an extension for packs like Dandelion and others which share their palette to suit your needs. But as said, that is a maaaaassive load of extra work.