A wonderful checklist of the Aldine “tip top” detective novels can be found at http://mysteryfile.com/TipTop/Detective.html.
Steve Holland posted a biography of Robert Prowse Jr. and his father, also a prolific artist of penny dreadfuls. This can be found at: http://john-adcock.blogspot.com/2010/01/tale-of-two-roberts-by-steve-holland.html
Holland writes, “It was around 1893 that Robert Prowse junior began his association with the Aldine Publishing Co., producing illustrations for their partwork publications of Burrage’s The Lambs of Littlecote and The Island School amongst many other contributions. His illustrations appeared in Aldine’s Garfield Boys’ Journal (1894-95) and Aldine Cheerful Library (1894-95), and he worked for most of Aldine’s library titles, becoming their main cover artist from the mid-1890s.”
“His work can be found on Boys’ First-Rate Pocket Library, Aldine Detective Tales, and Aldine Romance of Invention, Travel and Adventure Library in the 1890s. Probably his most famous covers were for the Aldine Robin Hood Library, and he continued to provide cover art for years to come, his last known work appearing on the Aldine Invention Library (1913) and Aldine Cinema Novels (1915).”
Note, the book covers really are blue, not just bad photography.