Xinerama setup for multiple DisplayLink devices:
#################################################

Section "Device"
        Identifier      "dl0"
        driver          "displaylink"
        Option  "fbdev" "/dev/fb0"
EndSection

Section "Device"
        Identifier      "dl1"
        driver          "displaylink"
        Option  "fbdev" "/dev/fb1"
EndSection

Section "Monitor"
        Identifier "monitor0"
EndSection

Section "Monitor"
        Identifier "monitor1"
EndSection

Section "Screen"
        Identifier "screen0"
        Device "dl0"
        Monitor "monitor0"
EndSection

Section "Screen"
        Identifier "screen1"
        Device "dl1"
        Monitor "monitor1"
EndSection


Section "ServerLayout"
        Identifier     "multihead"
        Screen      0  "screen0" 0 0
        Screen      1  "screen1" LeftOf "screen0"
        Option "Xinerama" "on"
        Option "Clone" "off"
EndSection

###################################################

Multiple screen (using an integrated intel gfx card):
###################################################
###################################################


Section "Device"
	Identifier      "intel"
	driver          "intel"
EndSection

Section "Device"
	Identifier      "dl0"
	driver          "displaylink"
	Option  "fbdev" "/dev/fb0"
EndSection

Section "Device"
	Identifier      "dl1"
	driver          "displaylink"
	Option  "fbdev" "/dev/fb1"
EndSection

Section "Device"
	Identifier      "dl2"
	driver          "displaylink"
	Option  "fbdev" "/dev/fb2"
EndSection

Section "Monitor"
	Identifier "monitor0"
EndSection

Section "Monitor"
	Identifier "monitor1"
EndSection

Section "Monitor"
	Identifier "monitor2"
EndSection

Section "Monitor"
	Identifier "monitor3"
EndSection

Section "Screen"
	Identifier "screen0"
	Device "intel"
	Monitor "monitor2"
EndSection

Section "Screen"
	Identifier "screen2"
	Device "dl0"
	Monitor "monitor0"
EndSection

Section "Screen"
	Identifier "screen3"
	Device "dl2"
	Monitor "monitor3"
EndSection

Section "Screen"
	Identifier "screen1"
	Device "dl1"
	Monitor "monitor1"
EndSection

Section "ServerLayout"
	Identifier     "multihead"
	Screen      0  "screen0" 0 0
	Screen      1  "screen1" LeftOf "screen0"
	Screen      2  "screen2" RightOf "screen0"
	Screen      3  "screen3" LeftOf "screen1"
EndSection
