The photo is on the back of the BB, it will not be on display.
Someone on another very recent BB thread (asking about what sort of disability a boy had if he could go to the gym and use a treadmill for ages) posted how to see the sex and month and year of birth of the person the Blue Badge is issued to.
Look on the front, at the top it says 'Front - display this way up.' on a fluorescent yellow background.
The expiry date is in a large font.
Under that is the long number you need to look at, it consists of six digits, a single digit and nine digits.
The last 9 digits are the ones with the information. I've not used a real badge for this, just made up the numbers, but it illustrates how the poster said it works. It does work to decode like that for a relative's badge.
If the last nine digits of the long number are 0867Y0919
08 would be month of birth of the BB holder, so August
67 would be year of birth of the BB holder 1967
Y would be female, X would be male
09 would be it expires September
19 would be it expires 2019
IF anyone thought a badge was being used fraudulently and IF they could get close enough to read that number or photograph it, they could just about guess if one of the people who got out of the car was that age and sex. But to do that, they'd have to be peering into the windscreen pretty closely, or maybe focusing while taking a photograph, either way their actions are likely to be seen as pretty much suspicious by anyone nearby.
If you want to report suspected Blue Badge misuse, type that into google and add the name of the local council where the misuse has been seen.
Some have a form, some have a hotline, some ask for these details,
The Blue Badge reference number, expiry date and who it was issued by
The registration number of the vehicle displaying the badge
Where the vehicle is usually parked and what times.
A short description of the person using the badge.