@sharprm: I am no lazy cow (), but well eh... I am just not skilled enough to push out graphics so fast... Your mockups really motivated me to continue with this. I used Arne's palette for the objects in the 2nd row, as I have big problems with colors. Restricting colors was a really good hint, maybe I should expand Arne's palette to 32 colors and recolor the existing stuff.

row1: Flint, Mummy, Incarnation, Princess Narkatete, giant bat, snake
row2: healing potions, whip, gun, ammo, dynamite, keys, treasure

I tried to shade the rocks of the golem...

@sharprm: Hey, didn't realize that you made another edit... This time, I really like your floor blocks! Very ancient! The lightning reminds me at a sundown, so maybe they could still be a bit too bright for the dark rooms of a pyramid. Well ok, depends on the torches and stuff. I will try. Actually, I have big problems with palette adjustments, so color reduction might be a bit beyond my experience level. But I really want to try that later, although 16 colors seem to be too few for the style i am looking for.

PS: I have found backgrounds of metal slug, even with a sphinx. But no mummies. Anyway, really great style! And beyond my abilities 

Thanks for your edit, sharprm. I like the skull and the shadowplay on your mummy!  Maybe it is so intense because your mummy is darker than mine. I tried to catch up a bit, but it didn't come out so good. Maybe I try again later.

Yes, my background is very poor and it was a bit too ambitious to call this a mockup. The floor should indeed look like sandstone, but your yellow is too bright. Maybe I should try a "yellow in the dark"...

Here are more mumbling mummy characters, which are based on an old Amiga game concept that never made it into a real game.  The game is about treasure hunting while malicious creatures and evil traps are waiting for our brave hero. A resolution of 256x384 or 400x300 should be reasonable, but I don't know what it turns out to be.

At the right is a raw edit of the first boss enemy who starts up as some plain rocks lying on the floor. Then the unknown mystery figure revives him and the rocks form a rock golem.

-All tiles are 8x8(actually 4x8 cos widthpixel),
-Also all tiles share the same 3 global colors (thats the first palette row below each mockup here)
-Each tile can have one additional individual color, the twist here is you can only use the first 8 colors for this.

Actually, you can even tell each block if it is a hires-block (8x8 pixels in 2 colors) or a multicolor-block (4x8 widepixels in 4 colors) in this screenmode. (That's why you can only use 8 colors - the 4th bit of the color nibble is used to switch hires/multicolor) It has been rarely used in games, because using individual colors for each block doubles the amount of bytes that has to be scrolled by the CPU. It can be found in games that use page-flipping (like Antiriad) or games that use special scrolling-restrictions (like Citatel).
Here is an example (the leaves at the right use hires blocks and the stones at the left use multicolor blocks. Yes, the red "ghost" is a sprite) http://www.thelegacy.de/pics/screen/a/antiriad-06.png

my favorite demo of that era was and still is HARDWIRED

Hey quite nice, didn't know that one. But it definitely cannot catch up with the mother of all Amiga demos: Kefrens "Desert Dream"
http://www.youtube.com/watch?v=GH2GyQQIBNo
EDIT: skurwy: oops, didn't see your post comming. Seems like I do not agree with you 
EDIT2: Wow, someone did a C64 version of "Desert Dream". Stunning!