Horror vacui describes a kind of art motivated by a fear of empty spaces—and a love of infinite detail.
The Book of Kells (ca. 800) glorifies God by infusing the page with layers of ornament.
Where’s Waldo (“Where’s Wally” in the UK) presents page after page crammed with figures.
In the back yard behind Tio’s Tacos in Riverside, California, the palm trees are festooned with small plastic toys or Barbie dolls.
The highly ornamented style is common among many outsider or lowbrow artists, such as S. Clay Wilson, Robert Crumb, and Robert Williams.
Wikipedia on Horror Vacui and Book of Kells.