And now a little more for the bitcoin-qt splash screen.
https://github.com/old-c-coder/bitcoin-git/commit/a3b0406c78c194a2925f627caefc0548fcaa012bJust a slightly modified splash.png that has a thin black border around it, so that when the splash screen comes up on a white background, which is not unusual with other programs running, it doesn't "blend" in and be hard to distinguish from the background. On a dark background it is basically is the same.
Qt is much like windows, one must recompile the file that loads the .png file (splashscreen.cpp or bitcoin.cpp in earlier versions )so that it becomes "incorporated"into the exe much a "resource" in windows.
Ron