abdul , first you'll need to extract and repair your current player's firmware. Guide here
http://www.mympxplayer.org/how-to-ex...tool-vt66.html
Next, you'll need S1res tool to modify the screen images, the guide is here
http://www.mympxplayer.org/how-to-mo...ool-vt206.html
Once done, save the newly themed firmware and re-flash the new firmware back into your player. Guide here
http://www.mympxplayer.org/how-to-up...ayer-vt46.html
There are many theme packs that you can download from the downloads section here
http://www.mympxplayer.org/themes-dc25.html
However, do take note. Do not use someone's themed firmware to directly flash into your player. You'll only brick your player if you do so. Rather, export their images and import into your own extracted firmware.