I also have a spec V, great all in one tank but its width makes it challenging. My spec V is pretty busy because I have shrimp and a betta together so I needed lots of hiding spaces for the shrimp. If thats not a consideration then this is what I would do (just my 2 cents since you asked).
1) Put the heater in the pump section, it will fit fine but you will probably need to lose the suction cup, its not needed anyway this gets it out of the way.
2) I would lose the thermometer all together, unless your keep your house below 60 degrees you will notice if your heater dies when you do water changes etc and that will be fast enough that your stock wont die off on you
3) Lose the statue it doesn't add realism or scale
4) Take all the tall plants and group them together at the end of the tank with the filter and outlet to provide a little forest like area for the fish to swim through
5) Take that moss ball out and break it apart. Take the drift wood out and super glue bits of the moss ball to the drift wood, use thin patches or else it will look too fluffy when you put it back in. (this assumes the mass in the tank is wood and not stone - see number 9)
6) Take your shorter plants and put them on the right side of the tank away from the filter wall. This will give you the "triangle" look that is so appealing to so many with the shorter plants leading to the driftwood leading to the taller plants.
7) Remove some of the floating plants, to my eye they look too numerous and are likely blocking a lot of light from the rest of your plants. Personally I always balk at throwing away my floating plants, but the darn things multiple so quickly. You can get the right effect with floating plants only having a handful of them, you don't need (or want) to fill the whole tank
8) Personally I don't like blackwater setups, if you do then ignore this piece of advice, but for me I would take the wood out and boil it to get rid of tannins. Obviously if you choose to do this, do it before you attach moss.
9) Not entirely sure what I am looking at, is the giant mass in the middle all driftwood or is it stone?? If stone you either need to remove some of it or all of it, its too big and is blocking the flow of the tank, if its not all one piece try putting in smaller bits, if its wood then try turning it a bit, so its not so high up.
10) As others have suggested you should fill the tank up to within .5" of the rim. Basically high enough so that your floating plants are not quite touching the lid.
Again just my two cents, I will be the first to admit I am not great at aquascaping, but I happen to own the exact same tank and have thought a lot about how to get the most out of it.