this reminds me of the funniest things i remember Garver saying on Miami Ink (i apologize for being a tattoo TV watcher). anyways, he was tattooing a tiger with cherry blossoms on some 18yr old kid and the kid's mom was there the whole time. as he was coloring it, he said he added the surprise of an all pink cherry blossom for the kid's mom. the mom thought it was cute and they were all laughing it off and Garver slips in, "what's wrong with pink?! some of my favorite things in the world are pink." The mom and kid didn't catch it and Garver just had a sly smile.
OK.. back to the topic. i was kinda interested to know when koi swim upstream, so i asked lord google and this was the first link: http://jamesthen.com/the-rules-of-the-japanese-tattoo/ there's a lot of information out there online, but as @Cork mentioned, the right tattoo artist will know these answers.
One of the right tattooers just so happens to write books. This is a good start for $20... Bushido: Legacies of Japanese Tattoos: Takahiro Kitamura, Katie M. Kitamura: 9780764312014: Amazon.com: Books
when i got my dragon koi from Jill Bonny, she let me know that it is actually a Chinese legend, not Japanese. makes sense, since the legend takes place in the Yellow River in China. mine has maple leaves.
you can try to find pics of body suit pics from reputable traditional japanese tattooers and see what kind of themes they stick with and what kind of themes they mix.
but again... find the right artist and trust 'em.