We have had this ugly air vent in our WC for years. I knew that when I get the 3D printer I have to do something to it. Since this is only a decorative piece and it does not have to protect anything and you can print pretty much any shape I was able to get creative with this. I saw a leaf like jewel in some tv show and got the original idea from there. It did not take long from an idea to a physical object. (Files: STL, Leaf SVG, Fusion 360 Archive)
First mockup in Adobe Fresco with Apple Pencil.
Give the lines some thickness.
Convert the sketch to vector graphics in Inkscape and save it to SVG file.
Import svg to Fusion 360 and add the final 3D shape.
Slice the 3D design in Prusa slicer and print it.
And the ceiling looks much better.