Mark, agree with Stephen. One of the hardest parts will be getting the site ranked for the city(s) you pick. Not sure if 2 posts per week (8 in a month) will be enough content at the beginning. You will also need to get some backlinks.
It's not that easy to get ranked for major keywords of popular destinations.
One idea - for the city you pick, base your initial posts on some up coming attractions / events. Use suitable keywords (phrases) and you might have better luck in the short term with the search engines. It's worked for my site, to some extent (still lots of room for improvement). Also set the site up with google analytics or some other stats, so you can see what keywords etc. are working
Using Flickr images is worth a go, just watch out for the creative commons as there are several types and some state not to be used for commercial purposes (but it is still classed as CC). I'm sure you have checked out Skellie's post on this.
As for templates. If you have not checked out Smashing Magazine, they have a few lists of templates. There are plenty out there, that are fairly easy to set up with ads.
Amazon has just released a new widget (carousel) which looks interesting and it should work for the type of sites you are thinking of. Even if they don't buy what you are showing, they may click through to Amazon and buy something else. This is something I need to optimise more on my site.