It's common in the mobage industry for artists to go uncredited, even on games they contributed a lot of art (contractual purposes).
If anyone knows who drew the tachi-e for Code Geass: Genesic Re;Code please share.

Note that I'm not talking about the banners you unlock from playing gacha (解放イラスト), because these are already credited. Tachi-e are the standalone images of characters standing.

I think it might be whoopin who did most the non-banner tachi-e but it's hard to confirm.