BLS has no separate occupation for illustrators. They are counted in Fine Artists, Including Painters, Sculptors, and Illustrators. O*NET's reported titles for the group include muralists, portrait artists and sculptors as well as illustrators, so the figures blend very different kinds of work.
The wage data comes from the BLS Occupational Employment and Wage Statistics program, which collects pay from employers and covers employees only. BLS says 58% of craft and fine artists are self-employed. For illustrators, that means the percentiles on this page describe staff illustrators, not freelance income.
BLS also notes that illustrators increasingly work digitally, drawing by hand and coloring in software or drawing directly with a pen on screen. Illustrators who also work in design or animation software can compete for graphic design and motion roles, which BLS pays more, as the comparison table shows.