#1) The cosmonaut was pasted by you on a white background because original image proportions were too rectangular? You can try to go into the backend of wordpress and click on Settings > Media and turn off the checkbox labeled 'Crop thumbnail to exact dimensions (normally thumbnails are proportional)' ..
Please be aware that when you change settings, the thumbnails do not automatically change. You will need to download a free plugin (http://wordpress.org/extend/plugins/regenerate-thumbnails/) which will automatically regenerate all your thumbnails based on the new settings.
If you open your theme folder and find functions.php at the base, there are pre-defined proportions for thumbnails. Right now they are set at 'width'=>465, 'height'=>346 .. pixels, and get scaled based on the number of columns in your portfolio, so if its 3-4 columns, the images get scaled down (proportionally) to 232px width by 172px height. This scaling is likely causing the blurry effect, since they are scaled within the browser. If you plan on using the 232x172 size (as now), then you should change the line below in functions.php (line 24)
$avia_config['imgSize']['portfolio'] = array('width'=>465, 'height'=>346);
to look like
$avia_config['imgSize']['portfolio'] = array('width'=>232, 'height'=>172);
You may also want try how the crop option looks (some love it, others hate it)..
$avia_config['imgSize']['portfolio'] = array('width'=>465, 'height'=>346, 'crop'=>false);
I am not sure what is causing different images to appear, but please try not to use single 'quote' (') or double quote (") inside your image title. Loose quotes are the enemies of most computer code, and once in a while when not filterer out, they causes all sorts of mayhem. I see on that page, two of your images have single quotes which escaped into the code. (title="It" s-rouge-#1-h930-01'="" )
Please try my suggestions, and let us know how they worked out.