Sound related

ringtones collection: http://onj3.andrelouis.com/phonetones/

iMy ringtones

.imy ringtones are text based files with polyphonic data. It often also contains light flashing sequences and vibration patters.

imy-ringtone-software.zip
imy-ringtones-collection.zip

Theme related

Flash Menus FAQ (esato)

- Exploit gif (crashes phone): se_exploit_planet-surfeu.de.gif
- 211 flash 2.1 menu collection 100MB

Custpacks

Custpacks are the third and finalizing part of flashing firmware. Used by network providers to ship customizations like branding, themes, pre-installed apps, etc. Customize yourself. For extreme UI skinning, see MegaPackDB3210
- ad-link removal
- version info
- modifications

Software

https://github.com/jindrapetrik/jpexs-decompiler swf flash decompiler
CodeClaw IC Manager
353_apfeditor_v1.1_962.rar
menu_editor.zip
Custom menu creator 2.7 link
Rotating logo creator 2.1 link

menu.ml edit

menu.ml edit + animated elf menu GUI
swf edit + (Adobe) swf/flash player (was there even a theme you could “play”?)
lang edit
icon packs / edit
elfs for skin customization
font edit
lighteffects edit
soundpack
drivers for camera, display

Remove provider logo by layout.xml

in /tpa/system/layout/layout.xml search for
<object name="StatusIndication">

change
<sett name="TitleMode" value="1"/>

value from "1" to "4". Save.

Remove scroll bar by layout.xml

in /tpa/system/layout/layout.xml search for
<object name="ListObject">

Change
<sett name="ScrollBarMode" value="2"/>

value from "2" to "0". Save.

Add language /T9

copy .lng and/or .t9 to 
tpa/preset/system/language/ and 
remove lng.dat and lng.lst (recreated on boot)
also add language entry to allowed_language.txt

optimize font

create lnk to battery menu

create customize_upgrade.xml with content 
<?xml version="1.0" encoding="UTF-8"?>
<customization>
   <mmi>
      <shortcuts>
         <shortcut>Settings_Battery_Id</shortcut>        
      </shortcuts>
   </mmi>
</customization>

and copy to tpa/preset/custom. reboot.
Now you can set battery link in activity menu with options
Off=deactivate
1=activate
2=activate shortly (should close automatically)

Source: https://web.archive.org/web/20080603060716/http://www.se-world.info/thread160552-Firmware-Modding-Akku-Menue-Verknuepfung-hinzufuegen.html

A2 / DB3210 / C901

C901

What is my phone's flashlite version?

FL 2.1
C510, C702, C901, C902, C903, C905, G705, T700, T707, T715, W508, W595, W705, W715, W760, W902, W980, W995

Fl 2.0
G502, K660, K850, W890, W910, Z750, Z770

FL 1.1
K770, K790, K800, K810, W880, W850, W580, S500, T650

So if you have a FL 2.1 phone(such as a C901), flash menus made for any other FL 2.1 phone (see list above) will also work with your phone.
So search for Flashlite x.x flash menus or search for flash menus made for phones of the same flashlite version as your model!

Use TinyFlashMenu to insert menu and standby files in themes without se theme creator.

There is A2v1 (DB3150) and A2v2 (DB3210) phones, succeeded by DB3350 (which are CID80+)