It is possible to change the titleset. As optiondialog crashes by changing the title set, you have edit the config file
Freeciv crashes also on my desktop pc, if a try to change the tiles set. Hopefully this bug is fixed in the next release.

Set default_tileset_name=
"amplio2" is the default tites set
"hex2t" is a square tiles set with isometric view
"isophex" is a hex tiles set with isometric view
"isotrident" is a square tiles set with isometric view
"trident" is a square tiles set with view from above.


Maybe i will add a new package containing some of the newest tilesets from http://freeciv.wikia.com/wiki/Tilesets#For_2.3.