Polymnia and Kleio are two of the nine Olympic muses. Polymnia is the muse of hymns, sacred poetry, and so on, while Kleio is the muse of history. (You can read more about both of them in this post.) I am still only in the very beginning of my journey to know these two goddesses, but I hope to add to this post as time goes on.
I have found Polymnia to appreciate offerings of light white or pink wines, usually those which have been watered down, as well as fresh figs. For incense I would suggest light, airy scents (but not necessarily floral). Something like sandalwood, perhaps. I have come to associate her with the colors light blue, grey, white, and a light sandy gold color. In addition to the symbols associated with her in antiquity, I also associate her with butterflies, and with the pitcher and bowl, two items many modern worshipers of the Hellenic gods often use in their devotions - either to purify before devotions, or to make libations at altars.
In antiquity Polymnia was known to wrap a long cloak or veil around herself. Although not something I have worked with yet, I do feel somewhat called to wrap in such a cloth before calling on her for inspiration.
Kleio I have come to associate with the colors orange, red, yellow, and gold. Strong, vibrant colors, as well as with lions. Offerings of frankincense. Strong spicy teas, and maybe coffee? Non-physical offerings of studying history, teaching history, and so on... although, that's probably an obvious one, considering her role.