The use of the first postcard to confirm attendance to a social function (written at work!) and the second to request some forgotten belongings shows not only that postcards were used to send short day-to-day messages, but also that the postcards available for this purpose showed international images.
The next two are interesting because of their content...
"I was surprised to have a nasty letter from you..." - oh, to have that letter!
...and the sauciest correspondence I have:
Dear old saucy
How are you getting on after your funny mood. You know what I mean at Yarmouth. On naughty naughty...
I am sure the postman was a bit speechless after reading this one!