Problem with images not showing up/ adding a size attribute

[munum]

Ok so i am definitely a beginner at this stuff but i installed the shop ok however at no stage have images shown on my shop site. i am uploading the shop to a remote hosting server. the address is:
http://www.munum.com.au/prestashop/

my main site works fine and the shop seems to have installed the database and everything just fine but no logo images have worked even during installation. i upload them fine but they never show up.

if anyone could help that'd be awesome.

also another side question: as we are selling tee shirts how do i add a field where users select small, medium or large sizes? i have added attributes but this doesnt seem to distinguish them properly. do i need to add each product individually as small, medium and large or do i just add one product? obviously i have different inventory numbers for small medium and large sizes so would need to break this up somehow.
any help would be great.