Anybody know how can we change the background of our webpage without using custom css from thesis options/design options.
If you're running the current version of Thesis (1.6), you can change the background color from the "Design Options" screen found under the "Thesis Options" menus in your WordPress admin area.
On the Design Options screen, expand the "Body (and Content Area)" section under "Fonts, Colors, and More!" heading. There you'll find some background color options.
To get more granular, check out the other sections on this screen.