On the whole, I like the way it looks. The entrance is very nice, especially those pillars. I also like the goddess' figure on the background wall.
I think you could benefit from some slopes. It might help to smooth the edges on the goddess. I also think it might look nice to have a smooth roof, but "stair like" bricks at your feet.
I'd also suggest using a wider variety of blocks. Sandstone slab looks wonderful, and you can make some great patterns with sandstone brick and slab combinations. Brown painted rune wallpaper fits in really well in this setting. You can also use palladium columns (but actuated) for another pillar option.
I really can't offer much more than that for appearances. It's looking pretty good, and there's only so much you can pull off with the interior of one ;D I'd also suggest taking a look at what other people have chosen to do with their pyramids. If I'm lacking for an idea, I usually use google. Here's
part of the interior for a pyramid-dungeon I built for a mod, if you're curious about what block choices I'd use.
Now, for my thoughts on the adventure map itself.
Firstly, if you double jump just right, you can get on top of the pyramid.
I would move the player sensors under the chests to the side a bit. It's a good idea, the way you're using them, but players (like me) might open a chest while it's a max distance, meaning they can loot the chest without ever tripping the sensor, which might lead to confusion later.
The puzzle for the keypad is a bit vague. The last clue is extremely straight forward, but filling in the middle digits seemed a bit off to me. The puzzle gave me which digits to use, but (personally) I felt it didn't help decipher what order the second and third digits should be in. Regardless, it is doable. My main complaint with it is that it is done via the announcement box. The puzzle is rather wordy, and they don't stay on screen very long. Since you can't press [enter] to see what was previously announced, you are forced to spam the button until you've thought everything through. Personally, I would just put the puzzle on a standard sign, so the player can read it at their own pace. That's just a quality of life change, though, and not at all necessary.
Other than that, I'd enjoy seeing different types of puzzles. Maybe something that utilizes the weighted pressure plates, more shooting puzzles, some parkour, perhaps.
All in all, great job! I look forward to seeing the other dungeons in your series ^.^