It depends what format you have output the template in. If you've made it into a .jpg (or .png), sure - you can bring it into Scrapbook MAX!. However, it will function as an embellishment or quick-page would (the individual elements you put together to make the template won't be moveable or editable on their own like they would be in a Scrapbook MAX!-made template). You can resize the image (i.e. the .jpg or .png 'template' you made in PS) to cover the entire page but again you won't be able to move the various elements within the 'template' as you would with a Scrapbook MAX! template. You'd have to put your photos and text. etc. on top of the image or within or in behind any transparent spaces you might have designed (in the case of a .png 'quick page').
Hope that helps and that I've understood your question! Please let me know if I can be of any further help...
If you design elements in PS but want to make a fully-editable Scrapbook MAX! template with them that you can use in Scrapbook MAX!, you can always bring the individual elements you created into Scrapbook MAX!, lay out your page or pages, then choose File > Export Template. (To insert grayed-out spaces for photos, simply add any photo to the page you are laying out, arrange it as you wish, then right-click it and choose Clear-image (you can even re-size the grayed-out space after clearing it). Also, choose Remove Photos after selecting Export Template)
Exporting your page or pages as a template will turn them into a fully-editable template that you can use again and again in Scrapbook MAX!. In this case, the elements will be moveable since you've turned your page into a .sm2t file.