The Day at the Lake contest made me think of cabins, boats and fishing particularly, although a day at the lake for me would probably be walking, photography, spending time with friends, just because I do not know how to fish.
I decided on the theme of fish because I thought I could do quite bright and vibrant with the colour choices and interesting shapes with the actual fish.

The hero design came out quite bright with all the fish swimming in a couple of different directions. I like this, but I think the contrast of the colours make it look more child-like, nothing wrong with that but its not generally the market that I aim for, so I guess I should keep this in mind in the future when I am playing with the brighter colours.
I tried some designs that used a single colour for the fish in the foreground then a contrasting colour for the background. I actually think that some of the darker colours worked well with this but I found the purple and blue combination to be particularly harmonising.
I tried the designs using the blue and purple combination, then tried them with a range of blue, purple and yellow backgrounds for this. I think this is interesting and I actually ended up submitting the blue one for the contest. I think I always think I need to enter the hero design I do for the actual challenge but all these designs do still follow the theme so I think sometimes a slightly simpler design may be the one to go for.
Finally a few blenders here with the bubbles, I think these are quite cute and work well, although again I think the contrast of the yellow turns it into more a child-like design again.