Please, protect your special treasures properly. It is sad when you see the damage that is done by moisture when something is saved in a plastic bin or perhaps left in a non-climate controlled garage, basement or attic. Mildew and mold not only look awful and cause damage....it stinks!
Here is an example of mold damage. This is a hand-painted (or colored) lithograph or print from the early-to-mid-1860s, based on the round gown of the woman's "costume". With a magnifying glass one can see that the bonnet and shawl were also of the same fashion period. Additionally, the male figure is wearing what appears to be a frock coat, vest and bow-tie-style neck cloth popular in 1857. The scene is a French or French-style garden that bears a striking resemblance to gardens at Versailles. With no documentation, all is supposition.
While the image above is after cleaning as gently as possible, you can see where the mold would neither (gently) brush off, nor "dab" off with paper cleaner. The paper is most likely acidic and it is fragile. It must have been quite lovely before improper storage.
This second hand-painted (or colored) lithograph or print has a scene that bears great resemblance to the Gardens of Versailles (France), Blenheim (England), and even Private Newport (Louisianna). It is of a later period, perhaps the mid-to-late 1860s, based on the oval shape of the woman's costume. A magnifying glass reveals that her bonnet is also of that same fashion period. Bonnets, caps, shawls, fans and other accessories were often used through several generations. Bonnets/caps could be refurbished with fresh ribbons, lace and/or flowers to make them more au courant. This piece was not as badly stained or damaged as the one above.
You can see some discoloration in the upper and lower right corners; perhaps damp caused color to bleed? It is easier to discern the "costume" worn by the woman in the scene, and you can see the elongated oval shape, not a full round gown shape. The elevated walk way with statues is much like those found at Versailles, but the fountain does not match those I could find....so far. This paper, too, is fragile; you can see a segment of the upper left has separated. This piece is more salvageable.
From this point, I'll need professional assistance to restore or conserve the salvageable piece. I don't know if anything can be done for the first; and if it ought to be done? Neither of these works are signed and there is no printed data either. The cost versus value will need consideration.