We do need a photo. What colour is the roof?

You can borrow wallpaper books from suppliers and compare some you like by holding the samples up to your walls. Be sure to test how well they complement each other at different times of the day under different light conditions. I know it's hard to know for absolute certain how a particular wallpaper pattern will look on a large scale, but it's a place to start. And the people at the decorator stores will be happy to advise you.

there are some interesting putty grey colours in the knots of your floorboards. I reckon it would be worth holding some paint swatches up to the boards and see if you can find one that ties in with those driftwood tones in the timber . Then order a sample pot in a half or quarter strength version of the matching colour then see how it looks. Otherwise it is so hard to go with colours people have named, as every space has different light. If you are happy with the colour of the floor boards, let them guide your choice and you can't fail (as long as not too dark). :)

Very light grey on all walls would be nice or white. Lighter colours like white tend to make spaces bigger and in ur case this needs to be done. The artwork on the weight bearing wall (in kitchen) needs to go as this draws ur eye to the wall . The railings on the stairs need to be painted (either colour of the walls or white)as this will help blend into the background and make the space look bigger.