There!! The photos are now visible. Help!!

I would start with the flooring - do you have ideas on what you want to do with that? LVP could be a good choice -

for the stairs sometimes it makes sense to just pull up the carpet, fill the holes, paint them and cover with a lovely runner.

Start with a commercial NICDQ designer who has access to contract level materials and who is familiar with all of the public access safety and ADA access requirements. Without that level of certification, you are opening yourself up to a lawsuit.

For sound muffling and slip protection, I think you need carpet on the stairs. Stripes wear well. I'm showing you runners but I would do wall-to-wall on the stairs. I would go with gray/brown/blue or a clay/brown stripe, and I might look for a narrower stripe than these

This below is called Cigar Box from the Andersen Carpet Marquet collection

or you could go warm

I think scuffs on the walls will show less with a textured look for the lower wall covering

with a glossy paint above in a slightly lighter but matching shade.

I think wall art will only clutter up the space. If residents would find it useful, a sturdy but small table near the door could be nice, like the one shown in the picture of the clay stripe stair runner.

It's very tempting to put some kind of mirror on the face of the upper landing, but it would need to be just the right one. Maybe one like this (MaryEllen via Wayfair)

If the condo owners at the top of the stairs can come to an agreement about what they might like on their shared wall, a pair of tall framed prints side by side might be nice. But it looks fine without art Again, if there is room and useful for the residents, a simple sturdy table for setting things down momentarily, could be a good choice. If the condo is where it rains a lot, som attractive shared umbrella storage might be really nice to have.

From Apollo Box, and they also come in black and white (maybe gray). I like them because they take short umbrellas as well as long ones.