Hi, Here is the design I came up with for your event. I wanted to catch all of the elements you mentioned, while keeping it as clean and fun as possible. Let me know if there is any restrictions as far as number of colors or gradients, and I will be sure to come with alternate design options as needed. Thanks!
I finally finished my new design for you! Phew! ;) Anyway, I noticed you need a clean, flat 3-color design for shirts, so that was the main thing I kept in mind. This particular design would be on blue shirts with 3 ink colors: white, yellow and sky blue. The shirt would show through to actually give a 4-color effect! I created 2 runners (male and female) running with the beach, water, sun, etc. in the background, as well as the famous Gulf Beach arch.
I will post a version on white next as well. I look forward to hearing what you think of this one!