Is it permissible for a woman to keep photographic images of herself with a trustworthy female relative? And does the ruling differ between pictures taken in childhood and full-adornment pictures taken in adulthood?

If the picture is in safe hands, preventing foreign men from seeing it, then there is no harm in keeping it with her, provided that it does not display what is unlawful for a woman to look at. If it is possible to take it from her without embarrassment, that would be preferable, because pictures of women often contain prohibitions. As for the picture of a young girl who is not usually desired, there is no harm in it, because looking at her is not unlawful, so long as it is not with lust.