If you look up Mercenaries of Earth by Tomas Braun, you will notice my covers all look the same but different. I designed the covers for that comic book look. DigitalDonna does the art work. Each cover was about $50.00. Donna Casey is great to work with but has became so popular there is a waiting list for her work.
Actually it is a good thing because it slows me down. If I did my own format, cover etc. I would be putting a novelette out there every two weeks. Better to space them about 6 weeks apart.
Are you getting signs made for the new books also? I love the idea of the magnetic signs. I've actually incorporated it into my second book. Not for advertising but for disguising the MC's vehicle. Today he is a florist tomorrow a plumber.
I bought signs for my first four books. That is enough. Once you find one of the books it leads to the next in the series. Not sure I want to advertise my Hospice series on my car. Cops would start following me, convinced I was a serial killer or something.