Graphs are generated via the GraphViz module. There is no way to exactly control the layout so results can be erratic, particularly for more complicated graphs. Also, there is no simple way to constrain the size of the graph.

Also, as you may have noticed below, schemas without any foreign keys defined look very silly.

Alternate layout

<%args> $s $neato => 0 <%attr> show_tables => 0 show_columns => 0