I looked around, and found a definition for spot/vignette/boxed/full bleed illustrations. If @will-terry, @lee-white or @jake-parker reads this, could you tell us is this definition is right ?! Thanks!
Boxed, Vignette, Spot and Full Bleed
(This may sound somewhat obvious, but it's worth clarifying!)
In classically constructed books, a "boxed" illustration has straight defined edges, possibly with a border or frame, and sits within the confines of the page, so there is a gap between the image and the trim (i.e. the edge of the page). The illustration might be cropped from a loose-edged original, or painted to a ruled edge. As the border encloses the scene these are particularly suited to images with a considered, balanced composition.
Vignettes are illustrations with faded or loosely defined edges. The loose edges incorporate the white of the surrounding page to give the image space, lightness and draw the viewer into the scene.
A spot illustration is a small free-floating motif, usually with no background. In picture books spots are particularly useful as visual addenda to the main narrative.
Bleed refers to part of an illustration that runs off the page edges, 'full bleed' means an image that entirely fills the page and is cropped by the trim. Nowadays very many picture books are full bleed throughout, however it's particularly effective when suddenly brought into play for the most dramatic and panoramic images.
