It seems correct. The last update from your VA was today. It shows 17 pilots, 717 PIREPs. That about matches what's on your site.
1. the logo and/or other images do not upload
I just tried this and it worked... you sure?
2. in the VA details page, the graph of daily pireps is inactive
It's not a daily graph, it's monthly. It's working on your page
3. when a pirep arrives, it is counted in the VAs list, before it is accepted. So, sometimes the flights number is not correct. If a pirep is declined, it still counts in vacentral, i think this is wrong
If it's rejected, the count is updated later on. There's a nightly process which reconciles all of these