I'd like to point out that there is a FreeDesktop.org specifications for icon set format that also specifies the pseudocode for icon lookup. Implementing that would let you use every freely-licensed icon theme ever created.
I believe using a pre-existing icon theme designed by professionals is a better idea than making your own. First, do you really believe that you'll do a better job at it than highly skilled professional designers who have spent literally years doing nothing but their respective icon themes? Judging by the fact that the icons shown above do not even stand out from the toolbar and because of that are not recognizable as interactive elements, I very much doubt that.
But even ignoring that, making a custom icon theme is little benefit for a hell of a lot of time invested. Making a complete icon theme is hard work and takes literally years, as well as hell of a lot of expertise. You know how many unique icons "elementary" icon theme has? 2976. That's almost 500 unique designs in 6 sizes (and before you ask, no, scaling an already designed icon is not easy). And that's actually the bare minimum for a fully functional desktop; Ubuntu icon set forked from elementary long ago, or Xubuntu icon set forked from elementary not so long ago are even larger.
TL;DR: "an obvious icon theme that's not ugly" is an already solved problem - see KDE icons, elementary icons, etc. Redox needs hell of a lot of things done specifically for it from scratch, but an icon theme is not one of them.