The planets and signs associated with creativity are Neptune, Venus, and the sun, and Leo, Pisces, and Libra (and occasionally Taurus). The fifth (strongly), 12th (moderately) and seventh (sometimes) houses also are associated with creativity.
The third house is connected to writing and singing abilities, especially if planets are there. People who are naturally creative or artistically talented usually have a strongly placed Venus (next to sun/moon/nodes, or on a chart angle) and planets or the north node in the fifth (and possibly the seventh or 12th) house(s). Multiple planets in Pisces, Leo, Libra, and occasionally Taurus can also do it.
Neptune in a prominent position can make someone imaginative, though potentially also dreamy and disorganized. A favorable (trine, sextile) connection from Neptune to Mars or Saturn results in more productive creative output. If Saturn makes challenging connections (conjunction, opposition, square) to Venus or Neptune it impedes creativity (and manifesting, especially if conjunct or square Jupiter).
All of these placements are consistent with someone’s destiny, however. If someone’s Saturn seems to reduce their creativity (or manifesting), they are a soul learning to take responsibility, work towards concrete goals, and approach things rationally.
As with manifesting, there are times and phases when all people are more creatively inspired, and these times have to do with transits involving Venus and Neptune.
I have long loved the concept of muses–I call myself “The Astro Muse” after all. Muses are, in essence, the mythical personification of inspirational energy. For many years, I thought a “muse appearance”, or inspirational moment, was a semi-random occurrence that could possibly be encouraged by creative exercises, rituals, and openness. There is probably some truth to that, but I blew my mind when I looked back at my astrology chart during periods of prolific artistic creation and realized they correlated to notable fifth house transits, Venus transits, and Neptune transits.
The progressed moon making connections to birth or transiting Neptune (or Venus) and Venus (or Neptune or progressed moon) transiting the fifth house create particularly muse-ful times. The north node transiting the fifth house (and less so, the 12th house) or making a conjunction with natal Venus are other signs the muse is near.