WordPress can handle photos from small thumbnail size to large full screen photos. However keep in mind that larger, high resolution photos will slow down your webpage loading times, which will annoy your users and may affect your search engine rankings.
WordPress photo blogs and websites with a large amount of images or large higher resolution photos should use an optimization plugin and a content delivery network to speed up webpage loading times.
The EWWW plugin is an easy to use optimization tool you can use for your photo blog.
MaxCDN Content Delivery Network
There are a number of excellent content delivery networks you can use for your WordPress blog. If your web hosting account does not include a CDN, you can purchase the service from a separate company. We like MaxCDN. They provide excellent service and support, and it’s very easy to setup their content delivery network with your WordPress site.