The Pre-Raphaelites proved to be an important influence on his early work as an artist. In 1857 Stanhope met Edward Burne-Jones who invited him to assist him in painting mural decorations for the debating chamber of the Oxford Union.

In 1859 Stanhope married Elizabeth (Lilla) Dawson, née Wyndham-King. The following year they commissioned the architect Philip Webb to design Sandroyd, a house for them at Cobham in Surrey.

As a painter, Stanhope worked in oil, watercolour, fresco, and mixed media. His subject matter was mythological, allegorical and biblical. He exhibited frequently at the Liverpool Academy from 1858 to 1863 and at the Royal Manchester Institution from 1865 to 1890. His work was also shown at Carfax & Co. Gallery, the Dudley Gallery, Grosvenor Gallery, New Gallery, Royal Academy and Royal Institute of Oil Painters in London; and at the Walker Art Gallery in Liverpool. He participated in the first two exhibitions of the Arts & Crafts Exhibition Society held in London in 1888 and 1889.

In the 1870s Stanhope began an association with the church architect George Frederick Bodley, and with him worked on decorative schemes including the chapel at Marborough College (1875-79), and Holy Trinity in Florence (c.1892–96).

For reasons on his health Stanhope often spent the winter months in Florence, Italy and in 1880 settled there permanently. He died at his house, Villa Nuti, on Bellosguardo, Florence on 3 August 1908.