Presumably you refer to the icons that appear on your Safari Start Page?
If the saved website icons have been replaced by single letters, you need to selectively delete a single corrupt cookie from your Safari cached data.
From iPad settings:
Settings > Apps > Safari > Advanced > Website Data...
Allow the Website Data list to populate. When the list appears, in the Search dialogue, enter "cdn-apple.com" (without the quotes). Only one entry should appear in the remaining list; swipe to the left, then select Delete.
Your Safari favourites page should now refresh. If necessary, force-close and re-open Safari.