Ok ! first of all you need these stuff

* Photoscape ( for making wallpapers adding icons and stuff resizing )
i will make a photoscape video guide for n900 wallpapers =)

* Queen Beecon Widget ! ( awsum widget i don't know much about it but it gets the job done )

* extshortcut ! ( for finding the desired app name easy way )

1. First of all make ur desired wallpaper with all the icons and stuff

2. now its time for using queen beecon widgets ! for example i want to make a widget for opera i will first select queen beecon widgets from the desktop editing menu go into the settings of Queen beecon Widget at the top you will see an option * show * open it and set it to hidden it will make ur icon invisible yet workable then at the right side u will see an option add cmd click it now

and copy paste into it the following command

dbus-send --type=method_call --dest=com.nokia.HildonDesktop.AppMgr /com/nokia/HildonDesktop/AppMgr com.nokia.HildonDesktop.AppMgr.LaunchApplication string:"<application name here>"

Example for opera i typed

dbus-send --type=method_call --dest=com.nokia.HildonDesktop.AppMgr /com/nokia/HildonDesktop/AppMgr com.nokia.HildonDesktop.AppMgr.LaunchApplication string:"opera"

now resize it according to the icon u made on your desktop and place it on it and save then press done and touch where ever you placed the QBW , it should open the desired app shortcut in my case opera

note : all shortcuts are case sensitive and even an extra space in the end will make the command wrong

for finding out the name of an app use extshortcut widget just add extshortcut go into its settings just below the type : Application you will at the right see browse u may need to scroll to the right if it isnt visible once you open browse all your apps will appear with the names you should put in the <application name here> just delete it after words its just an easier way of finding your desired app name

i tried explaining everything in detail !
hope it helps =)