This is a very romantic image, not so much in the relationship sense, but in the artistic sense--it's idealized and sentimental. This card is a departure from the familiar 3 of Cups of the RWS, which shows three women celebrating in a sort of folk dance, or possibly an elaborate toast. The dance shown in this card is more intimate and balletic. Even the background is romantic, with a misty river, a boat like the one in Waterhouse's Lady of Shallot, willow trees, cattails and the sort of improbable rock formations seen in Chinese landscapes. It's a bit like an antique oriental screen, and in fact, these dancers could actually be posed in a photographer's studio in front of a painted backdrop, rather than actually on some sort of picnic where they're having only three overflowing cups of something. Even the cups themselves are overstyled, with very long thin stems and impractically tiny bases. They'd surely tip over in real life.
I like the card but I'm not sure what bearing it has on my day. (Also a little disturbed that more I look at it, the more the male figure looks like Michael Jackson in his late 90s incarnation.)
If we consider Golden Dawn attributions, three is the number of Binah on the Tree of Life, whose name means 'Understanding.' It is the Supernal Mother or Great Female Force. Briah is the world of Cups, the World of Creation. So we have Binah of Briah -- the card is said to represent the fulfillment of pleasure and fertility. The goddess Persephone is associated with this card in Golden Dawn tradition, and that adds an element of enjoyment that cannot last or cannot be entirely trusted--after Persephone enjoyed the pomegranate, Pluto was able to capture her.
This Cosmic Tarot 3 of Cups does have a feeling of yearning after a moment that cannot last, even while living it. I often get that feeling when watching a dance of this type. The dancers are portraying the joy of the moment and also the mourning of its temporary nature. Maybe this is something that develops inside us as we grow older and more aware of our own mortality. You enjoy a moment and at the same time grieve for it before it is even over. You feel both at the same time. I can see that in this card. I've felt it many times. Enjoying a view, for example, you revel in it so entirely, but a part of you also feels regret that you will have to keep moving, or that the perfection of the light will sink into the darkness of night, or that you only have a limited number of days left in your life to see such things. It's all mixed together in that single moment. It's the sweetness of it. It's why we cry at weddings.