In the details below, I use something to stand in for the word I am looking for. Speech may have euphony; writing may have something.
For example, when writing about the relative sizes of items, I might prefer to use "gigantic" and "tiny" as opposed to "big" and "minuscule," for consistency between word length and meaning. This has to do with the way the words appear on visually the page, not necessarily how they sound. In particular, the words chosen have something because of their character (or letter) count.
Clarification: I suppose "looks good" would be the meaning I am seeking (euphony is basically "sounds good" / "good sound"). I am looking for a single word, though, that is specific to writing. A lot of things that aren't writing "look good."
In response to @Zan700: he picks out that my above example is analogous to onomatopoeia. But here is another example: I might find words whose characters are all the same height to be pleasing to the eye, so for a user ID, I might pick "neo" instead of "Neo" (as Neo does in The Matrix). For simlar reasons, I might use the verb "peg" instead of "spike," because "spike" is too spiky in appearance (spikier than "peg"). In this example, the chosen words have something because of the shapes of the individual letters.
Yet another example: in the following poem (yes, I checked the definition of poetry in the OED), the characters are arranged in a visually pleasing manner: the antecedents line up vertically, as do the consequents, etc:
first <- function(x)
if
(0 < x %|% length) x[[1]] else if
(x %|% is.vector) x else
NULL
Beauty is in the eye of the beholder, so some would find the following, syntactically and semantically equivalent poem more pleasing:
first <- function(x) if (0 < x %|% length) x[[1]] else if (x %|% is.vector) x else NULL
The preceding poems have something because of their layout.
So the meaning I'm looking for is "looks good," but not necessarily for any particular reason, just as euphony does not, in and of itself, have a particular reason behind "sounding good" (it could sound good because it rhymes, because of alliteration, or because it sounds like one's own name).
If there is no such word, perhaps I could invent one (say, for use as a proper name in a fictional story, or in a poem). Someone with better Greek could make a suggestion. Perhaps eumatia?