I myself was unsure about the exact phenotypical (the only word that I could think of that sounds better than 'description') definition of 'spare upper lip', and googled it. By going into images and typing ONLY 'spare upper lip', 90% of the images that appeared were Toby-related.
The upper part of this picture is quite accurate to the descriptions, i think But, the lower part, not so much See, in the book Four's seen as having a sparse upper lip and a full lower lip, but you've given him full lips!!!
actually nothing is accurate since hes supposed to have a hooked nose too, and stick up ears. its just the way imagine him, since english is not my first language when it said he had "upper lip to spare" i thought it meant big enough to spare XD everyone imagines characters differently