Hi Emelia,
How exciting to be getting your Spur Thigh (do you know what subspecies he is?)! Here are links to care sheets for the two most common species of Spur Thigh in case you don't have one already (Testudo ibera and Testudo graeca graeca):
https://www.tortoise-protection-group.o ... 014New.pdf and
https://www.tortoise-protection-group.o ... 014New.pdf
It's great that you have an open topped tortoise table set up, and a soil based substrate -- perfect. Regarding what else you can put in it, is that a water dish that I see in there (with a printed card on top)? That will be fine, but you should also bathe the tortoise a couple of times a week for 15 -20 minutes in lukewarm water just up to his chin (or where the top shell meets the bottom shell and in a container that he can't see out of, like an old washing up bowl), because some tortoises don't drink from their bowls and they can easily get dehydrated indoors under the lights. An added advantage of this is that they tend to poo and wee in the bath so there is less spot cleaning for you to do.
Yes the covered area is meant to be a sleeping area, but lots of tortoises don't use it, and they do tend to like to sleep in a cramped, cozy place, so he might well choose your bendy bark thingy to sleep in, rather than the covered area. In fact, you could just leave the cover off and he can use that more in the daytime. The substrate you are using is absolutely fine, and just make it as nice and deep as you can (3 or 4 inches if possible), as they like to burrow down into it.
It's nice that you have the stones in there (different textures to walk on, etc.), and you could even put a bigger rock or stone in -- something to block the sightlines, as tortoises get a bit bored if they can see from one end of the enclosure to the other without interruption.
The main thing with tortoises is to get the temperature right and to provide a good source of UVB. What sort of bulb are you using -- is it a UVA and UVB bulb or just UVA, and what wattage is it? If it is one of those all-in-one mercury vapour UVB bulbs that is good, but it needs to be the correct distance from the floor of the table, so check the manufacturer's instructions. If it isn't a UVB bulb then you will need to provide a source of UVB, and we can advise on that. He will also need a good calcium/D3 supplement to sprinkle on his food (they need huge amounts of calcium and the UVB reacts with cells in their skin to produce vitamin D3 which enables them to absorb and utilise the calcium).
Regarding temperature -- this is really key to everything! Tortoises are ectothermic, meaning they don't make their own body heat like mammals do, and reply completely on the temperature around them to make them warm enough, allow them to digest food, etc. So you need a good thermometer, and you need to measure the temperature directly under the heat source, and at the height of your tortoise's shell. You want to aim for around 30C under the lamp and around 20C at the cooler end (and no extra heat will be necessary at night, as they are used to a drop in temperature at night (but it shouldn't go below around 14C or 15C).
A thermometer mounted on a wall near the lamp will not give you an accurate reading, so you either want a temperature gun, or what is easier and cheaper is one of those digital fridge-freezer thermometers with a digital display unit that can sit outside the table and then a probe at the end of a cord that you can hang down into the table near the circle of light given off by the lamp. Something like this:
https://www.pharmacy-equipment.co.uk/pr ... er-tmm105/ You can get them in lots of places, but be sure that it has a Max/Min facility, as that will tell you hot hot or how cold it got since you last looked.
It's also important to be able to raise and lower your bulb to increase or decrease the temperature as necessary, because the temperature in the table will definitely be affected by the temperature of the room (if it's a hot day then you will need to raise the lamp a bit and if it's a cold day then you will need to lower it.
Will he have an outside enclosure as well? Tortoises love being outdoors and the UVB from the sun is of a higher quality than what we provide indoors, so if he can go out on a nice warm day then that will be great.
Sorry for such a long email and hope I haven't put you off! It's just that it's easier to tackle any potential problem early on, rather than wait until the problems get bigger. It would be super to see a photo of him when he arrives. Have you decided on a name yet?
Nina