For translation instructions and the syntax of files to modify:
http://www.solarus-games.org/doc/1.0.0/translation.html

List of images that contain text:

- \c languages/XX/images/action_icon.png:
image containing all the possible variants of the action icon
(the blue icon in the game):
  - Confirm: validate a choice while saving the game
  - Next: show the next message during a dialog
  - Info: in the inventory menu, show information about an item
  - Back: get back to the game after a dialog
  - Check: look at an interactive element in the game (like a sign or a door)
  - Open: open a door or a chest
  - Action: activate an object
  - Pick up: lift an item like a pot, a bush, a stone, etc.
  - Throw: throw a lifted item
  - Grab: grab a block
  - Stop: stop an ongoing action (like using an item that consumes magic points)
  - Speak: talk to an NPC
  - Change: change the value of an option in a menu
  - Swim: swim faster in water

- \c languages/XX/images/sword_icon.png:
image containing all the possible variants of the sword icon
(the green icon in the game):
  - Save: save the game
  - Back: get back to the game after a dialog
  - Confirm: validate a choice while saving the game
  - Skip: skip the current message of a dialog sequence

- \c languages/XX/images/pause_icon.png:
image containing all the possible variants of the pause icon
(the orange icon in the game):
  - Pause: pause the game
  - Back: unpause the game

- \c languages/XX/images/floors.png:
image containing all possible floor numbers that can be displayed in dungeons:
  - B16: sixteenth basement floor
  - B15: fifteenth basement floor
  - ...
  - B1: first basement floor
  - 1F: first floor
  - 2F: second floor
  - ...
  - 16F: sixteenth floor

- \c languages/XX/images/gameover_menu.png:
image displayed when the game is over:
  - Game Over
  - Save and continue
  - Save and exit
  - Continue without saving
  - Exit without saving

- \c languages/XX/images/pause_submenus.png:
image containing the background of each pause submenu and its title:
  - Inventory: title of the inventory submenu, that displays the items found by the player
  - Map: title of the map submenu, that displays the world minimap or the current dungeon minimap
  - Quest status: title of the quest status submenu, that displays the equipment, the pieces of heart and the finished dungeons
  - Options: title of the options submenu, that lets the player configure the video mode and the keyboard and joypad commands

- \c languages/XX/images/title_screen_initialization.png:
image displayed when the program starts, before the title screen
  - Zelda Solarus presents