Hi All,
1)From Setup, enter Tabs in the Quick Find box, then select Tabs.
2)Click New in the Custom Object Tabs/VisualForce Page / Web tabs related list..
3)Click the Tab Style lookup icon to display the Tab Style Selector.
4)click Create your own style on the Tab Style Selector dialog to create a custom tab style if your org has access to the Documents tab.
5)Click the Color lookup icon to display the color selection dialog and click a color to select it.
6)Click Insert an Image, select the document folder, and select the image you want to use.
7)Select a file and click OK. The New Custom Tab wizard reappears.
Now you have create your own custom tab style.
Hope this will help you in solving issue.