I like a lot of the ideas you have with your sigs but the disproportionate fighter images kind of kills most of em.
You seem to have good skills creating backgrounds (I really like the Lytle one), which is always a challenge (and one of the harder things in my opinion) when creating a sig so you're definitely off to a good start, just get the proportions right on your images and those will be awesome. Dont try to make the image fit the sig, make the sig fit the image. Starting with a good, high quality and good lighting picture is the best advice I can give you; It'll make your life soo much easier.
You seem to be mixing it up as well, which is awesome and something a lot of experienced graphic artists dont do enough. You're off to a great start and I look forward to seeing what you can put out in the future.