Hi Amy, Isn't Houzz fantastic - it's easy to spend hours here looking at ideas and hearing other peoples ideas. If you've not already done it, get the high pressure hose out and give the pebblecrete a clean to get the colours to come up (give the lower stones in your retaining wall a clean up too so you can check their colours). Looking at the colour of the pebblecrete now and seeing that the area will be shaded for at least part of the day and you won't want it to feel too dark - especially in winter, I'd go for the sandstone look unless it's completely at odds with the retaining wall. Most places selling pavers will sell you or give you a single paver that you can bring home to check the colours in situ. I'm sure that it will look fantastic when it's done.

Here is the trim colour - to help others out. and in use...

Both suggestions above are good. One house we did had an outdoor deck area which led to a pool and we put timber decking on the deck with a perpendicular timber-decked walkway leading to the pool. We then put lights in the walkway which created a 'catwalk', continuing along the deck. It looked great at night lit up with the pool lights on too! Love the stepping stones and gravel idea too.

a thin layer of gravel in a border of your left over bricks would be quick, cheap and OK to walk on if the under surface is level and compacted..or giant concrete pavers or new railway sleepers could look interesting and re-use as many of the existing bricks as possible to connect with the area outside