In this blog it is described how irregular or not plain background is erase using pen tool.
- Open image in photoshop with irregular background. any of the image you shuould take with irregular background.
2. select pen tool and select outline of cat.
3. select whole cat(you can zoom in and zoom out while selectiong) then click ctrl + click. it select cat
4. press ctrl + shift +I to inverse selection then delete it and you get image without background.