Upload & Sell: Off
If there were some way to record your images on mud bricks, then you could hope for at least 3,000 years of proved archival storage.
Unfortunately, your question is all too pertinent. There are so many ways for digital archiving to go bad, and digital change moves so quickly, that promises of digital permanence seem foolish. It is a major problem. Even paper offers better proof of permanence than anything digital storage can now offer. So for your best images, printing them out using archival pigments and acid-free cotton paper, then storing them properly, is probably your current best hope of letting someone see them 300 years hence.
One possibility that might be interesting, maybe even commercially, would be some variation of the earlier manifestations of the analog technicolor process, where color images were rendered onto three strips of black and white film, one for each primary color. Because of the inherent stability of silver oxide emulsion, that process offers the prospect of very long-lived archival color, maybe limited only by the durability of the substrate. Silver oxide on mud brick might really get the job done. I haven't heard that anyone is proposing to do it though.