You can set "endsround" "1" in either the base or the flag to make it force the end of the round.
Looks like you're missing a texture in that first screenshot. The theme is kind of odd... the textures don't quite seem to go together. Also, it looks very blocky. Especially with the rock textures and grass. It doesn't look very natural. Also, having huge groups of entities like you do can cause major problems with lag and framerate. It's better to spread things out so only 4 or 5 are visible at once, or spawn with some equipment and just have a couple upgrades lying around.