If you do a simple update to ICS, you won't lose data or pictures.
If, however, you decide to do a factory reset before or after the update (which, for some people, has helped with performance improvement), then you will lose all data and apps. If photos are saved to your external SD card, they won't be lost, but I think they might be at risk if they're on the internal memory. Your app list is saved to Google Play and/or Amazon Appstore (depending on where you got the apps). If you selected to back up data and settings to your Google account under Settings, then things like your wifi passwords and menu settings will be saved and restore automatically after the reset. Anything from your Google account (e.g., Google Music, Gmail, Google Contacts) gets quickly re-synced to your phone after a factory reset.
Sent from my A100 using Android Central Forums