Boot artwork is not customisable.
The X windows centered background image on a white background
noxbg boot option makes the X bootup screen blank.
Otherwise the background logo is retrieved from $HOMEPAGE/bg.png
Users see the artwork set in the the X background when the Web browser is reset and re-initialising. Not when Webconverger boots the ISO image. In practice users should not see Webconverger boot from cold start.
Therefore the artwork can only be seen between sessions. The amount of time this background is viewable depends on the speed of the computer. I.e. how long it takes to load the browser.
Example
So the default HOMEPAGE=http://webconverger.com/ So view the current background.