In this thread you can see anthropological difference between Latvians and Lithuanians, because they aren't exactly same. Photos are taken from this site: http://www.lt-lv-forum.org/
I have attributed ethnicities to people according to their names and surnames, described below photos in original site. Not always it is reliable way though, because sometimes both names and surnames can be both Latvian and Lithuanian. But usually it is not so, usually it is possible to see, which is Latvian and which is Lithuanian name or surname. Another problem is that some individuals might be of mixed Latvian-Lithuanian ancestry.
But otherwise, I think this could be quite informative thread
In order from left to right.
Latvian; Lithuanian; most likely Lithuanian (by name and surname could be also Latvian, but look-wise he is more like Lithuanian)
2 Latvians, 2 Lithuanians:
Lithuanians (standing in right side) and Latvians (standing in left side, sitting in first row):