set multiplot layout 2,1 margins .1,.8,.05,.95 spacing .05

$map2 << EOD
0 0 5
0 1 4
0 2 3
0 3 1
0 4 0

1 0 2
1 1 2
1 2 0
1 3 0
1 4 1

2 0 0
2 1 0
2 2 0
2 3 1
2 4 0

3 0 0
3 1 0
3 2 0
3 3 2
3 4 3

4 0 0
4 1 1
4 2 2
4 3 4
4 4 3
EOD

set multiplot layout 2,1 margins .1,.8,.05,.95 spacing .05
plot '$map2' using 2:1:3 with image
plot sin(x)*cos(x)**2, tan(x)
unset multiplot

$map2 << EOD
0 0 5
0 1 4
0 2 3
0 3 1
0 4 0

1 0 2
1 1 2
1 2 0
1 3 0
1 4 1

2 0 0
2 1 0
2 2 0
2 3 1
2 4 0

3 0 0
3 1 0
3 2 0
3 3 2
3 4 3

4 0 0
4 1 1
4 2 2
4 3 4
4 4 3
EOD

set multiplot layout 2,1
set size 1,.75
set origin 0.025,.25
plot '$map2' using 2:1:3 with image
set size .85,.25 # <---
set origin 0.025,0
plot sin(x)*cos(x)**2, tan(x)
unset multiplot