I'm pretty sure there are lighting and perspective mistakes on the tower, but I cant put my finger on it.
For pin-point accuracy and understanding of objects that cannot be found in real life. Create sculptures that replica what you want to draw or your own visions, then shine a light in the direction of your choosing. Take a quality photo, (or just draw in the room with it) then use that reference to fully understand and develop your vision.
For times like this when you are having difficulties.
Hey I think one of the problems you are having is you haven't really defined your light source. It looks like its coming from the left on the stairwell and the pathway but not really on the tower. I did a quick paintover to try to move you in the right direction. The whites are to white though! Also the tower has to be lighter its to dark not enough atmosphere to push it back.
PMMurphy: Thanks for the idea, I think that would work out very well! It also sounds very time consuming, so maybe rather for an illustrator than a quick design sketch (quick- haha, but I guess getting faster comes last for now)
tjmsaint: Thank you so much for the paintover! I'm always so happy to see people took my stuff and improved it, it really helps me too!
Now I did see your message only after I finished working but it showed me I had too few atmospheric dense in the midground so I added some. It already payed off, thanks alot! The lightsource in the new picture is dramatically different though...
So yeah... I looked back at the picture and thought the motive of this tower would look way better with rule of thirds, sooo.. here it is took me maybe 4-5 more hours... probably even longer and Im lying to myself. Well theres always room for getting faster when I got better right?
Hey! It's looking better already. The more time you spend the better. The thing that bothers me with the new one is just the 2nd closest tower. It looks to cut and paste from your first with the path going in the opposite direction. Maybe try to make a thin rampway from the first to the 2nd? Im not sure but I would at least change the path to the tower on 2nd and maybe the structure a little bit. Even if they are all the same building it might look better with a slight modification of it. I would also try to show a little more light source in the clouds on the left. That will integrate your highlights on the tower with the background a little more.