<snip>
..
.
$perc50=(img50 int)/$total;
You can do it per day, per month, per year, per 28 days, per PMS cycle, per anything you want provided you have the data to do it.
</snip>
:) this is the part where i am a bit confused actually, can you give me one or two examples and i'll work from there?
What you have to do is get all the pictures viewed for a specific day/time frame (you said this was all tracked in a DB anyways) and then add up all the totals and perform the same calculations using the views all added over the days all added.
$img1=img1 int day1 +img1 int day2 +img1 int day3 .... img1 int day30
$total= img1 int day1 +img2 int day 1+img3 int day1 +...img50 int day30
$img1perc= $img1/$total