If I were a paying customer, I would be happy with your army cake. I know the number of stripes is wrong, but it is cute and does the job. And it looks neat.
I would, honestly, be disappointed with the Minnie Mouse cake. I like most of it, but the major issue is that the top tier is bulging. Professionals know how to make their cakes so they don't bulge.
Please don't get offended - my goal is to be able to make and sell cakes to a professional standard as well, and at this point, I am not ready. I am making some cakes for friends' children (only VERY good friends) and family members to practice. I also make one or two cakes a weekend, at least, just for practice. This is expensive, but if I want to get good, I have to try what I see and ask questions. I use dummies, but also real cakes because I have to see how they behave under buttercream, under fondant, today I worked with modeling chocolate and almost had a nervous breakdown trying to get my BC smooth. Groan!! My husband eats the cakes or I end up throwing them out, but I have to spend the money and practice!! I also bought the Wilton Butter cream class online since I can't get to classes in person, and it is a great class for the $19.99 and I am taking a cake decorating class at the Culinary Institute of America next week. For one day it is very expensive, but the school has a great reputation and I want to learn the right way to do things. I really can't afford it, but I can't afford to waste money on classes that are not worthwhile, and I do believe that I do best with good teachers.
So I would say practice, practice, practice!! In the last month I have spent at least 60 or 70 hours, probably more, just working with the materials and making cakes. That is not including my working on my scratch recipes and finding awesome buttercreams that don't use crisco 'cause I hate that. I think your cakes are mostly neat, very clean, nice looking, just a few issues. So if you want to get better, you know what to do. And make sure you charge a fair price, to yourself!! I made a cake today with chocolate ruffles all around, yes, it was my first time, but it took me about 6 hours. Unless I get $120 for a cake like that, after supplies, I would be making minimum wage. Not going to do that. Nor should you. You are spending time and money to learn, so honor that. If someone doesn't want to pay you for it, they can go get a WalMart cake, and you will find your customers who value your expertise.