In general, the only way that photomosaics are actually effective is to have a high enough resolution (i.e. large number of tiles) for the picture to be recognizable. Here I have taken a photo and made it in several different resolutions just for comparison.
Do you know what this might be a picture of? First we have 5 tiles across.
Next, we go to 10 tiles across.
It should start to be a little clearer now…
Next is 20 tiles across.
I’m sure you can see it now…
Just for a really nice finish, here is 40 across.
And just for complete clarity, here is the original.
Thanks to Brinkidink for the link to this beautiful photo!