Thank you! Just synthesizing together all the stuff people have offered so far, with a little seasoning of my own added.
Good, yes. I was saying not a tapestry because it needs to be more permanent. Carving or mosaic tiles are either one better ideas.
NOW... I'm an idiot for not having looked at the map closely enough. There is no tower, just a dungeon. Gah. I will rewrite my intro/background to fix that.
As to your suggestions for the entrance, overall I like it! I think we need a few changes to clarify some things and expand the descriptive text. How about this:
As you hack your way past vines and undergrowth you see the entrance. Huge double doors sunk into the rocky hillside, with broad, ancient steps leading up to them. Though partially obscured by dirt and debris you can see that the floor is figured with mosaic tile, an abstract pattern of red, orange, and white squares which form wavy lines leading toward the doors.
The doors themselves are huge and grand. The pair span a full eight feet wide and are almost ten feet tall, and are made of what appears to be planks of some strange orange wood; the joints between the planks curve strangely, even though the doors' edges appear straight and square.
The doors are made of a wood more than twice as hard as oak, and they swing inward, preventing their heavy iron hinges from being attacked. However, the door is secured from the inside with a heavy but old and rotten oaken bar, so that forcing the doors is actually no harder than usual.
The large wall to the right is covered in carvings which depict battles between men and trolls. One wizardly figure appears throughout, leading the fight and casting mighty spells against the trolls; the last image shows him being crowned. The care put into the carvings, still easily visible after what must be centuries of neglect, indicate their importance to the people who built this place.
The floor is covered in dusty mosaic tiles depicting the sun and the moon, and between them a constellation of eleven stars, with a background of pure black tiles.
The spear trap is activated by pressure; each character stepping on it has a 1-2 in 1d6 chance of tripping it, with 1 added to the range for each additional character in the space (so if four characters occupy the square, the chance is 1-5 on 1d6). Roll each time a character steps on or off of the space. When the trap is activated the spears spring up from the floor through small tiled panels that rotate out of the way, and each character or creature in the affected square must save vs. Death Ray or take 1d8 points of damage. The trap can be detected, but not disarmed, as the mechanism is entirely hidden. Once activated, the trap will reset itself in 2d6 rounds.