Dear Ferenc,
you can, of course, also use the Do command to create a list. There are different ways to do this and it is certainly easier to use Table. If for some reason you need to use Do, then something like this might work for you
Manipulate[Module[{v}, v = {{0, 0}, {1, 0}, {1, 1}, {0, 1}};
Graphics[Reap[Do[Sow[Line[{v[[i]], v[[1]]}]], {i, 1, n}]][[2,1]]]], {n, {2, 3, 4}}]
M.