(1) The white background you refer to may be the frame (evident in image #2), in which case you can set imageFrameStyle="NONE"
(2) Here is a quote from the description of the enableMouseWheel option from this page.
Setting this to true may affect scrolling of the HTML page that contains SimpleViewer. Mouse wheel scrolling may not work on all OS/browser combinations dues to a limitation in the Flash Player.
Other than setting enableMouseWheel="FALSE" (default setting), you could disable the scroll bar on your page with this CSS code:
... with the consequence that if your gallery is too large for the user's browser window, then the user will be unable to scroll down the page to view the complete gallery.
Otherwise, you could set your gallery's width and height (and the dimensions of all parent containers) in percentages rather than fixed pixel amounts and the gallery would dynamically resize to fit in the user's browser window (with no scroll bars) like this example gallery.
SimpleViewer Support Team.