Yes it is possible to persiste customize object in view 
state, Supposed your are having one variable named x for 
which you want to persist the view state.

dim x as integer
ViewState(Value) = x  

Which can then be accessed as follows: 

x = ViewState(Value)
  

You have to use <Serializable()> attribute prefixed to the 
class declaration before you keep object of this class in 
viewstate.  However, larger the object, slower will be 
performance.  There will be risk of viewstate getting 
corrupted.  

Eg
'' in class definiton:
<serializable()> Public Class Fruit
 private sName as string
 public sub new(ByVal Name as string)
    sName = Name
 End Sub
readonly property Name as string
  Get 
    return sName
  end get
End Class

''in code behind:
if page.ispostback = false
   dim MyApple as new Fruit("Kashmiri Apple")
   ViewState("oMyFruit") = MyApple
end if

'' In button click
label1.text = ctype( ViewState("oMyFruit") , Fruit).Name