@vdhulst I have updated the logo in the SlicerAstro extension and I created a full customized SlicerAstroApp. See below:
Linux binaries will be soon available at Releases · Punzo/SlicerAstroApp · GitHub .
It will be nice if you or Leon can check the compilation/packing on MacOS (all the necessary steps are described in link).
Next step would be to update all the icons in SlicerAstro, but it is better to wait to see if the 3DSlicer icons will be redesigned as well (see Update Slicer's icon set) and have the same theme.