You can switch between various player skins without patching the firmware. I have included few skins below:
How to install:

1. Download the KD player from below.
2. Copy it to your cell phone.
3. Install it.

How to apply skins:

1. First copy the skin files to your ‘Other’ folder in your cell phone. (Copy both kdi and kds files)
2. Start the KD player.
3. Once main menu appears, go to menu> more> Change Skin > Open Skin File.
4. Now keep pressing select until you reach the ‘Other’ folder where you have stored the skin.
5. Select the skin and apply it.

Files:
KD player 0.8.6 for 240*320
KD player 0.8.6 for 176*220
KD player 0.8.6 for 128*160
KD player 0.8.9 for 240*320
KD Player 0.9.6 for 240*320

Skins:

176*220

My Chemical Romance[new]
NBA skin[new]
Zune
Leopard Twilight
Media Center
New Years 2008
Chocolate skin
Christmas Skin
Kmp skin
Blue Crash
iPhone Black
iPhone normal
Dead Leaf
Cocamusic
PSP Skin
Splat
Real player skin
Walk The Beat 176*220
Walkman v2.0
Walkman v3.0
KD Player Black Skin

240*320

Xmers (transformers skin) [new]
DS Toad Steps [new]
WMP Fractal [new]
Microsoft Surface Adaptation [new]
Windows Mobile Skin
iMac skin
Media Center
Play Now
New year 2008
Chocolate skin
nVidia Skin
Christmas Skin
kmp skin
iPhone Original
iPhone Black
WMP11_Aero 240×320
PSP 240*320
SteelV2
CocamusicV2
Alienware adaption
Walkman v3.0
Real Player
Walkman v2.0
KD Player Black version
iPod Black
iPod Blue
iPod Green
iPod Landscape
walkman_2_boss
Grey glass
Zen
Nike Black
Nike Orange
WMP 10
Keep walking

128*160 Screen Resolution

Kobe_Bryant [new]
Chocolate skin [new]
Christmas Skin
Splat
iPhone Desktop
iPhone Black
Walk The Beat 128×160
Walkman v2.0
KD Black version

Special Thanks to sriramkris06 for creating wonderful themes