With all respect, I have the feeling that my comment is not going to be so different to what you have being said to, but here it goes.
A full Visuals/Art asset pack that works for a full game and at the same time being reusable to other projects doesn't look so feasible for me, imho. I mean, while that's what most of us may want... and the idea of having GUI, sprites and 3D models all artistically homogenous is mouth-watering and all, at the same time we all want to make our games different to the rest.
What about focusing in some specific areas in particular?
You have been already recommended with complete GUIs and looks like a good point (buttons, fonts, window-borders, window-backgrounds, sliders, radio-buttons, ... )
But after checking what you offered for free, what about sticking with that? Making specialized packs with those? Personally, I liked the little guy and made me remember those RollerCoaster Tycoon little people. Well, actually most of you offered in the pack. :P
What about plants? Animals? Vehicles?
What about making separate packages with what you already offered? Tiles on one, buildings on other, a bunch of little people on other, etc...
I've the impression that offering a good amount of tools and assets to choose from makes developers interested. And well, I hope that's easier to achieve than big full-game scale artistic packages.
I hope this answer helps you a bit and I wish you a lot of luck!