Hi Justin,
Generally I use the rule if the keyword helps to describe the image then yes.
You can get away with putting in a keyword if it's not, but that might skew results in your web stats if people are finding that page wrongly.
Basically the bounce rate is taken into consideration, this is where someone goes to a page then leaves it very quickly, so they bounce off the page.
That counts against you, so you want to make sure that if they find that page with the image on it that it has relevant content to what they were searching for, so in your example Jacksonville-florist might be what they were looking for, but they see a surfboard and think oh that's not what I was looking for and bounce to find something more relevant to the search.
So be careful how you name files, sometimes it's best not to stuff a keyword in where it's not wanted or needed.
Also Paul is right hyphens should only really be used in the file name, but you will also want to use them in a URL.
Google treats Hyphens as spaces, but it also helps with browsers that there isn't a space in the url as they then replace a space with a horrible looking %20 which makes the URL harder to read as a human.
Hope that helps.