If I run a gallery site in php with no mysql requried can a shared host handle the traffic? let's say it receives 20k+uniques daily
I don't think it will be able to support 20k Unique even without mysql. Get a vps or something if your gona get this sort of traffic
This depends on the shared host you choose. Some hosts oversell, and once a site uses to much of the system, they boot them. It also depends on what kind of content you are serving up. I would still say though, with the relatively cheap prices on VPS right now, that may be the way to go. Reason being, a cheap web host, will charge you $2/month, then kick you off, a decent web host, may charge you $20/month, and you'll be Ok, a cheap VPS, could run you $20/month or less as well, and then you'll have complete control over all the resources.
It mostly depends on the limits each individual shared host gives each controlpanel / main domain! I would recommend that you go with some Managed VPS hosting for a more reliable and stable experience when browsing your website.
I think it all depends on the Hosting. If all those images are not copyrighted I think host gator shared hosting can handle that much of traffic, but it's only maybe If get that much traffic I think you can already afford to get a VPS or DEdi Anyway for a start I think shared hosting is always the BEST option.
the providers will not want you to use too much of their resources even if their server would allow without much trouble. get a vps.
I suggest to go for a VPS instead of shared hosting. With shared hosting if your host find high usage from your account they may disable your web site and you may face down time in your site. Kailash
You can use shared hosting but you need to setup an offloader. Offload your images to another server to split the dynamic pages serving and static content. You will gain more performance. You may use service like Amazon S3 with cloudfront or using steadyoffload.com service.