i'm trying to use Photoshop to create the main webpage for me with cool effects, and put my game onto it so as to have a rather more colourful
background. In photoshop, everything is in picture format (isn't it?), and
Only "mostly." And depending on what you mean by "picture format."
I was thinking of how I could use it as my webpage? Do I save it as a JPEG and then insert it in the HTML source code?
That is the most simple and direct of routes. In the old days we did it like so
<BODY BACKGROUND="my.jpg">
That will still work, but kids these days have a new fangled "right" way to do it with CSS.
You'll want your image to either be "kinda big" or designed so that it tiles nicely. I supposed you _could_ resize the browser to fit your image size, but then I'd have to scorn you. You _could_ run the game in a new window which is sized to fit. That would be a little less scorn-worthy. If you are getting in to CSS, you could use the background as only in the DIV which contains the game... Oh, and I think CSS has a no-repeat option (don't forget to make the edges of your image "nice" and don't forget to set a background color).
http://developer.mozilla.org/en/docs/CSS:background-repeat seems to be a fairly nice reference.
PShop also has image slices and ways to attach urls to image parts... All "stuff gruhn doesn't know about." It's there. I think it isn't what you want.
PShop won't do fancy Flash animations for you (I really really don't think) but then, you've got a whole game going on, so I suspect you are looking for a static image.
Remember: if you get wild in PShop with layers and whathaveyou to save the image as a .PSD to work on in future when you decide to change the image as well as a JPEG for use on the web page. Actually, not even if you get wild. You'll probably end up saving the JPEG out at least once as a "test" or "proof of concept" or "I just wanna see how it looks". You should (as a general rule) never repeatedly save and open a JPEG. Work on your master Photoshop file and save off JPEGs to.. display.