What a wonderful space! I agree with above, pick some large planters in a color you love. (I know this sounds crazy, but I have an inexpensive plastic/composite planter from HD that I prime and spray paint - allowing me to change the color whenever I want). But, looking at your previous sitting area, I can see that you might want something grey or black to go with your modern vibe. Everyone always mentions area rugs, but I have no desire to step on a wet, soggy rug! Just adding some planters, table accessories and sunshine and green grass will make a huge difference - meanwhile......impatiently waiting for winter to go away.

I think the furniture is fine add the panters and you pillows ans see what else you might need. Are you going to replace the cover you might look for one in a stripe .

Is there electric so you can run lighting for evenings? If not, solar might be an option. Perhaps you could add a few cushioned ottomans for extra seating. https://www.allmodern.com/outdoor/pdp/venice-ottoman-with-cushion-tkcl2164.html?piid=18354234

Or a pouf like this. https://www.allmodern.com/outdoor/pdp/zipcode-design-ayala-outdoor-pouf-ottoman-zpcd2071.html?piid=22110942

You modern furniture and tables all have hard heavy lines. Some soft greenery in planters will help but maybe for extra seating some chairs similar to these at Target. https://www.target.com/p/latigo-3pc-all-weather-wicker-outdoor-patio-chat-set-tan-threshold-153/-/A-51267971?ref=tgt_adv_XS000000&AFID=google_pla_df&CPNG=PLA_Patio+Garden+Shopping&adgroup=SC_Patio+Garden&LID=700000001170770pgs&network=g&device=t&location=9029555&gclid=EAIaIQobChMIgNi0nfTJ2QIVRmB-Ch1SpAXTEAQYASABEgJn8vD_BwE&gclsrc=aw.ds

You have to click on the link in my post. It takes you to the Target website. Works for me.

Target seating.

When you want help make it as simple as possible for us to see the pics . IMO you buy the best outdoor furniture you can and that would not be from Target.

I love the original rectangular planters! We have a variety of contemporary pottery that would look lovely in this area! They are a little more costly but they are made of the highest quality of terracotta that will last a lifetime and won't crack or crumble. Below are our Kito in Etrusca that is beautiful for modern designs. Have fun designing your area!

Although it is a much larger investment than you mentioned wanting to make, this space looks the perfect foundation for an outdoor kitchen. You could install a simple 7-foot island (like the one pictured) so you can grill out and enjoy it under your beautiful pergola! If the pergola is sound enough, you could also consider hanging a nice swing to match your existing furniture?