Many Overworld structures just aren't that interesting as far as loot goes, and I feel the desert pyramid falls in that category. 1.20 definitely helped matters with suspicious sand and dune trims, but I think it could also have something more unique than yet more pot sherds.

To this, I suggest the bottomless sand bucket, a renewable source of sand with many uses.

Sprite for the bottomless sand bucket

Obtaining

Each desert pyramid has a 40% chance to contain a bottomless sand bucket in exactly one of its chests.

Functionality

When you first find a bottomless sand bucket, it'll be at max capacity, holding 12 stacks of sand. Like a bucket of powder snow, you can right-click to place sand. This is helpful for pillaring, filling holes, or just storing sand, though you won't be able to bridge with it.

There are a few ways to put sand into the bottomless sand bucket:

• If you're holding the bucket in your main hand or offhand, any sand you pick up goes into the bucket.
• If your inventory is full, any sand you pick up goes into the bucket.
• Like with a bundle, you can put sand into the bucket in the inventory.

If the bottomless sand bucket holds fewer than 2 stacks of sand (128 blocks), sand will automatically generate in the bucket at 1 block per 15 seconds. This means that 2 stacks of sand can be generated over 1.6 in-game days.

The amount of sand in the bottomless bucket is shown with a blue bar representing 10 stacks over a green bar representing 2 stacks. This helps to communicate the sand generation mechanic — sand only generates to fill the green bar (i.e., only 2 stacks).

Conclusion

I think this should be added to the game for three main reasons:

1. It adds some uniqueness to the desert pyramid and more variety to structures in general. I think Minecraft's structures need more exclusives, things that can only be found at those structures. And while trims and pot sherds provide this to some extent, structures could do with some more unique loot when possible. This is a good starting point.
2. It acts an easily accessible shulker box of a versatile block. This is convenient in so many ways. Need to fill a hole without filling your inventory with stacks of dirt? The sand bucket is here to help. Want an easy option to pillar up? You have the sand bucket. Need to place large amounts of sand for a farm without cluttering your inventory? This is perfect for that.
3. It acts as a small but renewable source of sand. The bottomless sand bucket can generate 80 blocks per in-game day (provided that it's frequently emptied). This is a convenient infinite source of sand to have, especially for the early-game and mid-game, but it's not going to be revolutionary for your concrete megastructures. This whole item focuses around being nice to have, and I think this aspect strengthens that focus.

Please tell me your thoughts in the comments!