I recently needed to upload User Detail (User_Detail_vod__c) records for a whole country including user pictures encoded in Base64. Therefor I received all the pictures as JPG (with correct dimensions of 160 x 120).
It turned out to be really a complex process to get these into the system.
First issue was that I needed to write some code to encode all of them in Base64 and to receive a CSV file containing the codes.
When trying to map the Veeva User IDs to the files/codes I was facing another issue:
This CSV file can't be edited then in MS Excel because the Base64 codes can easily exceed the character limit of an Excel cell (32767 characters). This means that the codes are cut off when opening the document or when importing the data into Excel.
In the end I needed to utilize LibreOffice which has a higher cell limit, but it is not really a good alternative when working with a large amount of data (low performance). Also not sure if all possible codes fit into this limit.
For an IT skilled person this might be manageable with some effort, but it is really awkward.
Either end-users should be able to upload their photos themselves or a business/delegated admin should be able to do for them in bulk (without having deep IT skills).