I doubt if TIE fighters would be floating around the Emperor's tower at that point of the film when there is a huge battle going on (wouldn't they be busy elsewhere?).

The ideal time to show TIEs that close would be just as he is settling in as an extension of the honour flight they threw for him when he landed or maybe a few during the scenes where Vader pays a visit where we see them outside the tower.

I'd recommend using VLC for screen captures as you can maintain the aspect ratio and there are a lot of pictures of TIE fighters out there if you want to search for them pointing in almost any direction you can imagine.

If you are using Photoshop to make your mockups adding a little motion blur to the fighters and adjusting the lighting will make them look more cinematic.