First time painter, so I'm happy with the results so far but uncertain how to finish. I'm shooting for a more arctic-snow theme. I am not sure what color runes or wash to use

Golem - brown or fleshtone wash should be fine for the metallic color you chose. The skirt could be washed with a thinned down blue. I'd go black on the other metallics.
As for the runes, bright blue will complement the bronze best in my opinion.

Base - I would texture the base with some Vallejo texturing paste, then paint it light blue, wash with a blue wash/ink and drybrush back with the light blue, then white.

Afterwards add a shrub or two, ideally yellow in color. Mix some PVA glue and water 1:1 and sprinkle on some model snow. Sodium bicarbonate works as well but might yellow over time. I put together a short write-up for some simple base types here on the IA forums. https://community.fantasyflightgames.com/topic/220204-polda-paints-more-ffg-plastic/?do=findComment&comment=2229133

Put some snow on the golem as well. But go light.

Example: https://i.imgur.com/c4TY1w2l.jpg