Interior finishes are a personal are some ideas for inspiration.

...sealed concrete floor

sealing a concrete floor rather than cutting and polishing is a cost effective solution to maintaining the benefits to thermal mass in concrete.

...timber floor

recycled timber floor, or new timber floor that is plantation grown or sustainably sourced, is available in various widths and species for a wide selection.

...ply ceiling lining

ply ceilings, commonly installed with a shadowline expressed join adds warmth.

...timber wall lining

by using timber wall lining internally, the outdoors and indoors can seamlessly align.

Sealed concrete floor finish

recycled timber flooring by Energy Aspect Living

ply ceiling lining by Energy Aspect Living

timber cladding inside by Energy Aspect Living