Gnomes are steampunk/cyberpunk depending on the setting. Dwarves are art deco

I’ve always used art-deco designs when working on my gnome inventions in DnD… it’s a little wrong for proper steampunk stuff, (no steam engines in DnD) but a mixture of clockwork and art-deco makes for some really great designs.

Dwarves still have decoration, both in their craft and in their style. Braids, carving, etc. Brutalism does not have the intricate design dwarves seem to. It’s all big and blocky.