You don't mention whether you have to take everything out at the end of he day, or whether you can leave things in situ.
You can be quite creative with lighting effects. A lamp placed on the floor, inside a wicker or lacy shade creates interesting light and shade. I have one from Ikea in the corner of the room, placed on its side at an angle on the floor.
You could add pools of light with small table lights as well as warm glows with salt lamps. If you use an led lamp you can drape a sheer fabric over to diffuse and colour the light - just be careful to check the fabric doesn't get hot. You can improvise with a tissue paper over a bin with an led torch inside. Battery fairy lights inside a jar is another atmospheric effect.
A large pot, bowl or ornament will also add "warmth". Have a look in your nearest TK Maxx. Drape it with battery fairy lights, or position it with a little ikea lamp it will look even better.
I have zen gardens dotted around including beneath my couch breath hole for something better to look at than dust bunnies. A Japanese zen garden usually has sand raked into a pattern, plus some sculptural objects such as natural wood or stones and ideally something that adds another dimension, such as sky reflected in water, or flames for meditation/contemplation. Mine are very simple just a plate, bowl or other container with some pretty objects placed in.
It's great fun and can be done with just a few objects placed in a shallow bowl. Think marbles, crystal chips, fir cones, walnuts, teazels, led battery fairy lights, salt massage balls, pretty stones, tiny fossils.
If you have a diy bent you could try your hand at an indoor water feature with an aquarium pump and a pot filled with water and stones.
Can you hang pictures? IKEA has some great display/picture frames which could be used as shadow boxes to display some of the objects listed above.
Fabric adds softness, cosiness and warmth. Think about your couch set up. I have a pretty duvet cover under my towels to add colour and create drama. I use sarongs like sheets to contrast with my towels. They weigh nothing and often save me washing a towel. You could add a pretty cushion on your client chair or couch or some floor cushions in a corner. A fabric hanging would also work well, you could just have a pretty shawl folded and draped on a wooden hanger on the back of a door or hang any fabric or rug on a simple wall fixing.
You can't burn candles, but candles still make lovely displays either unused ones, or part burnt candles from home.
Screens also add a nice touch. If you look on eBay you can get nice Indian carved wooden ones for around £120 new. Just having one part opened creates a cosy intimate feel. Japanese style ones cost a lot less.
Have fun xx