As an example of the idea I had of using some graphics from OpenGameArt.org at least as placeholder graphics until a pixel artist comes along, I took some of the tiles from this sheet and adjusted them from the old EGA palette to the base palette I'm using
But it would still take quite a bit of work to look good. Atm the stuff just looks pretty strange/unpolished, and I doubt it's worth the effort to fix those graphics. We do have PAC-MAN-RED now, so a pixel-artist did actually come along. Sure, it can be a placeholder, but then again everything can be, even if it's just single color blocks. I'm not sure this is worth editing and integrating into the games when it will be throw out in the end anyway. But that's up to the coders to decide.
That is exactly how my palette is arranged.
Oh, and here's an adjusted palette for Little Green Quak-Quak using 12bit colour values instead of 24bit. I don't know why the palette uses 24bit colour values if the game is intended for a system with 12bit colour.
Because I don't know anything about bits and the likes; I just draw. I pick my palette with a ROM matashen gave me, wich lets me mix colors in handy. I mix them, take a screenshot and take the values from that.
Colors may get awry a bit through through the process of copying and pasting through several graphics until I'm done with my pixel stuff. May have happened here; usually the Lynx still displays them fine though, as they are only a little off and the Lynx displays the next possible value I guess.
About your palette: not sure if the colors are strong enough. You must imagine a huge lightsource behind the screen, brightening every color, making it lighter. Your red for example may look rather beige or so on the Lynx screen. You must always pick colors stronger than you intend them to be.