Ranked Data Newbie - please help!

#1
Hi,
I recently ran several focus groups where particpants were asked to rank a series of 18 photos from most natural to most unnatural. I then gav each photo a score from 1-18 (1 being most natural and 18 most unnatural). The data looks likes this:
photo 1a 1b 2 3
1 1 1 1 1
2 7 8 10.5 2
3 2 4.5 3 5
4 13 10 6.5 9
5 12 12 6.5 6
6 14 14 12 7
7 11 13 13 13
8 5 6 2 4
9 9 4.5 14 10
10 15 16 16 18
11 3 2 4 8
12 18 18 18 16
13 16 15 15 15
14 8 11 10.5 11
15 17 17 17 17
16 10 9 6.5 12
17 6 7 6.5 14
18 4 3 9 3
(with 1a, 1b 2 & 3 being the four groups)
So, now I would like to test for significant differences between each group. However, a sI understand it, all the non-parametric tests order the data from lowest to highest as the first step and with this data this means that it all looks the same! Any help would be gratefuly received as I am compltely stumped!

Thanks in advance
Kate Walker