I once had a very long, dark, narrow hallway I loved. Our first real home, half of a mission-style duplex in Hollywood. All bedrooms opened off it and had windows to the south, so THEY were beautifully sunny. It jogged at one end to the bath, so views toward both ends were of blank walls. We were such poor kids that I focused every cent on the rest of the unit and did absolutely nothing in the hall, literally the original bare bulb on the ceiling as the only detail. Not that I'm recommending that, but the cool quiet (wall-to-wall in this days) "minimalism" set off all the sunny prettily decorated other rooms extremely well and, not least vice versa. It made a pleasurable transition because it was so different, and I even sat down in there now and then just to enjoy its special quiet-far from the busy life everywhere else inside and outside on the street. All a way of leading up to the idea: could your hall be developed to serve as a wonderful complement to the rooms that open off it?

I would not put anything opposite the collage you have now because your hallway is too narrow. Some people like to move as far away as possible from such displays to take the pictures in as a group. That wouldn't be possible in your space if you had stuff on the opposite wall--- they might back up to see one wall and knock things off the other one. In general, if you have a hallway width less than four feet wide you don't want to line both walls with anything. If you have a long hallway or one punctuated by doors, you can put a grouping on one side, then hang things on the other side of the hall, not opposite but further down, iykwim. I would use a nice painting or print at the end of the hall, unless there is something you want to reflect from the other end.

How wide are your hallways? I haven't knocked into wall art in any house, and I've spent a lot of time in older homes, which are often scaled smaller than average. I would hang art. Whatever that is to you. Textiles, paintings, photographs. Your entry is an introduction.

Wood floor? Fabulous idea that will add value to your home! Next priority would be lighting. One dome light doesn't look sufficient for the space. I'd spend my budget on the bones of the space (doors, hardware, lighting, ceiling texture (?)), rather than dimensional decor, per se. Yes, you can add a piece of art at the end of the hallway but I wouldn't add any frames to the side walls. Too narrow a space to appreciate art, imo. Wallpaper or colour is a good idea as long as it relates to the rest of the space.