This is the sort of thing where, in my opinion, you’ve got to go all or nothing. I like to harp on gratuitous replacement of item icons (sometimes the battle screen as well) that hacks do too often for no other reason than “I’m making a hack; it’s got to be different”. But if you don’t have a theme you’re willing to commit to or otherwise some sort of ethos behind the design decision (I dunno, maybe you added red/green/blue backgrounds to the weapons because the weapon triangle is super important to the game’s design), I’m going to assume it’s arbitrary.
Behold a screenshot of a dead project:
I’m very proud of this stat screen, even though it’s mostly just me riding on the coattails of the main menu background from FE13. Other than Garcia (I didn’t get around to inserting portraits, which had darker colours), what’s the thing that sticks out? The affinity icon, the only unchanged element (well, ignoring the arrows, bar underneath the “Personal Data” text, and “1/3” thing, which are of no consequence, and the fullwidth font for LV/E/HP). Now, I love customising fonts. I will spend unreasonable amounts of time staring at each letter to make sure they’re esthetically pleasing when they line up (this one’s actually old enough that with my current standards, it should go back to the drawing board). But since I changed the font to have only a shadow instead of a border around each letter, it doesn’t look as good with the vanilla FE8 stuff. Like you, I was going for a more dark and moody esthetic. But as soon as you leave the stat screen…
Bam! Illusion broken. It goes without saying that I was going to change the map palette, map sprite palette, menu graphics, etc to match. I just didn’t get around to it. One more screenshot from another dead project:
In this project, I was trying out a new style for mini portraits. Instead of universally being 64×64 cutout ->32×32 mini sprite, they were resizes+stylizations of just the head area. I still like how they look, but since I didn’t change the mini portrait box (it was going to be something darker and more minimalistic) they look very out of place.
So, yeah. Either embrace the ＥＳＴＨＥＴＩＣ or go for “less is more”. I love customising every element of my game too much, but the less-is-more route has its merits: you have to do less work and it’s easier to call the player’s attention to new stuff. Say you gave affinity an important role in gameplay (weapon triangle’s for nerds! fire/ice/wind/lightning/water affinity pentagon time!); using new icons in an otherwise vanilla stat screen would make them jump out at the player and remind them that they’re important. I’ve actually seen games that move the affinity icon next to the character’s name; this would work, too. If you have some gimmicky new weapons the player has to watch out for, giving them custom icons will make them pop out as well.
And, well, if the text is what you need to stick out…