Answers to your questions

One of the first interrogation is about the new colour of the wall and the colours of the artwork that was to be installed there. "If I trust you, we can mix anything" said my correspondent. Indeed, everything can be mixed. But it is necessary to pay attention not to mix everyone! In the examples below I show different paintings on a coloured wall. Even though the paintings’ types and colours are completely different  they still are in harmony because the colour influences the colour. In these examples the warm tones are more in evidence because of the red wall. I photographed the same paintings on a neutral wall and it is obvious now that the reds are much less in evidence. Look at these examples. 

The other question that was raised is the format choice. "Isn’t it nice, for my birthday my spouse bought me an artwork, it is lovely. It is a large size and our house does not have many large walls. Where can I hang it so the painting will be at its best ?" It is indeed a very nice gift that you have received (what a good idea !). Concerning your "problem" I should say it is a "happy problem". You don’t have to live in a big house to be surrounded with large format paintings. They should only be displayed on the right walls. Some times a wall just a little larger than the artwork will be the ideal place. In other situations if you place smaller formats around the larger one it can create an environment that will bring attention on the larger one. For a better understanding, have a look at the images below.