An almost square platform made for a swing, house four sacred figures, Linga (aniconic form of Siva), Parvati, Ganesha and Nandi (Siva’s vahana)
The scene is Ganesha is worshipping the Linga with Parvati and the Nandi joining Ganesha. So far I have not come across any mythology behind this shrine.
The book Die Anderen Gotter, edited by Cornelia Mallebrein, has a complete example (with a swing) Page 186 and figures 112 and 113. In that example, Parvati is replaced by Annapurna.
This shrine is a seven cm by seven cm square. It is from Northern Maharashtra. It may date to the nineteenth century.
As usual, folk-Vigrahas are high on my list due to their simplicity. In this case, the similarity with one of the published semi-classical example of Gauri, Ganesha, Linga and Nandi is worth noting. Photo of that example reproduced below.