I have an interactive perl script which uses data from mysql to generate many plots through the Chart::Gnuplot package. There are times when the graph size is overloaded with to
I don't know if this would help, but...
plot [0:1] [0:1] NaN title "Hello" #Just the label in the legend.
or...
plot sin(x),NaN title "Boo" #Plots sin(x) (properly labelled) and a second label "Boo"
Of course, this still has the border and other things. You can unset those...unset border
and unset tics