You are already on the right track. Donate the six existing planters at the top of the stairs to somebody else. Even the largest of the six is too small. Replace those six pieces with two or three large ones and rock them out with seasonal color. You could even do a couple of larger pieces at your back entrance as well.

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I agree with K& D LM about the planters and would definitely add at least one by the door as well as up at the top. You don't have any photo looking down the stairs at what a visitor sees approaching the door, and I would love to see that.

The other thing I might address is the bare concrete wall. My first choice would be a good looking, weather resistant handrail to help out anyone from toddlers to folks with creaky knees to poor balance or vision. Depending on available space, a piece of wall hung seasonal decor or artwork such as a wreath or some tiles might help. You don't want it to look too busy, however, so see what it looks like with the added handrail. You may want an ornamental light fixture near the door , depending on what is behind the person taking the first photo.

some ideas