Hey, not bad. Here are a couple suggestions: Try to insert an actual logo in the header instead of the plain yellow text. It'll give the site more credibility. The categories dont look like links -- make the text bold and change the color. These two changes will vastly improve the design.
Nice and inviting theme... I agree with the comment above... Your logo (page name) need to stand out more. It is not readable with this yellow on that background. It can stay in some light colour. Some almost white would be nice if it gets a soft shadow behind to lift it. I would also lower it a bit to be on over the trees/water... I guess you want to try to rank in Search engines... Then some small steps to start with... You don´t seem to have changed the permalinks to /%postname%/. Do this in Wordpress Dashboard --> Settings --> Permalinks (then you get the post name in the URL of the posts instead of just a post number.) Some other SEO considerations: metatags and descriptions... (if you have not installed the plugin "All in one SEO" - I would recommend you to do it). Another thing: Your home page is very loooong... Apparently this is not liked by Google for ranking... Don´t ask me why?
Design looks like it was made 15 years ago.. Check "Css heaven" web design gallery for inspiration how to update your web design
Is this website just a sample site for prospective customers to view? I agree, the yellow header doesn't stand out like a header should. I reckon a banner would be better than just simple text. Just my opinion.