Hi,
Today, I tried to install another Moodle. And I got the same problem (again!) : images not showing up after a fresh installation.
The first thing I noticed is: when you have to fill the page admin user, the "star" for the required field is not displayed (text "required field" appears instead).
BUT I found the solution : when I created the config.php file, I choose "UTF8 format". The moodle's files are in the "ANSI format". I created another config.php with the correct format and the same installation works !
Maybe last year, I did the same mistake ...
NB : If you have completed the installation, it's too late : you have to start again and create the config.php in the correct format.