To use the start button, download StartAllBack, and under "Taskbar", set the start button icon to startbutton.png.
It should be easy to adapt to other programs like Classic Shell (uses a slightly different resolution I think) or Start11 (haven't looked into that one myself). If you make an alternate version or want some help doing so, send me an email at [email protected].
I've also included the GIMP file. I had to squish the legs to fix a graphical glitch, but you'll only see the legs if you make the taskbar taller anyway. Original and squished versions are inside it as layers.
Original pixel art used with permission by danatron1: https://www.reddit.com/r/mylittlepony/comments/11xi8a4/sweetie_bot_pixel_art/