That is a window manager known as TWM. you can change it:
As the vncserver man page states, applications that run at startup
are located in ~/.vnc/xstartup . Just change the default "twm" to
something more of your liking (for example "blackbox").
~willieray Registered Linux User #371168
Computer Science is as much about computers as astronomy is about telescopes
-- Edsger Wybe Dijkstra (1930-2002)