BoxFit.contain; size them from the outside with a SizedBox or Positioned.
ConversationBubble
Hand-drawn speech bubble marking conversation surfaces — conversation-starter cards, history day tiles, and the daily-summary header. Source:conversation_bubble.dart · asset assets/images/ConversationStarterBubble.png.
StyledListTile.conversation renders it automatically as the tile’s right-side decoration.
LetterDoodle
Hand-drawn envelope marking letter/check-in surfaces — the letter’s history card and the check-in letter detail header. Source:letter_doodle.dart · asset assets/images/Letter.png.
Why widgets for two images?
The wrappers give each mark a single, findable identity: usage is greppable (ConversationBubble vs. a raw asset path string), the asset path lives in one place, and future treatment changes (recoloring, animation) have a home. Follow the same pattern for new illustration marks.