Hello Harika,
There are multiple options to achieve this.
One is to create a custom log in page in your model and add it to your navigation in combination with using an image on your page, where you can select background image.
Another option is to change the standard .html page that mendix ships as standard sign in page, you can find this page in your project directory.
Under theme > web
Other options can also include css styling.
Hope this helps,
Good luck!
Hi Harika Bandaru,
In the Above Answer She used "IMAGE" widget you can find it in tool Box just search image.
Thankyou.