Alright, the main thing about all of these sigs is blending. None of the renders blend in to the bg. Remember, when making a sig, you are trying to make it look like the render belongs in the bg. Also, your bg's are really plain, you might try and add some c4ds, clipping masks, etc. And most of your renders seem really blurry or low quality. And alot of times your renders dont match your bg either. But you do very good text, (Better than me). And I noticed that are (As most people do when they start sig making) you are saving your sigs as jpg. Try saving then as png.
Hope I dont sound mean or anything, but this is all the advice I got when I started.