You can absolutely print 12x12 on your 1280, as long as you have 12x12 paper to print on!

When you go to print, choose Properties. On the main tab, change the media type to whatever type of paper you're printing on (if it's Epson's 12x12 Scrapbook paper, you need to choose Matte Paper - Heavyweight. Next, click on the Paper tab at the top. Under Paper Size, click on the drop down arrow and choose User Defined at the very bottom. Enter in the size of your paper (if you are printing on 12x12, enter in 1200 for the width and height - it is in .01 inches). Name it "Scrapbook" or "12x12" or whatever, and save. Then click ok. Now go and choose that paper from the list - it will be there from now on, at the bottom of the list. If you are printing on 12x12 paper, you will also need to go to the bottom where it says printable area, and choose Maximum and Centered (ignore pop up message by clicking ok).
Just so you know - the 1280 can NOT do a borderless 12x12 print, unless you are printing on 13x19 paper (if you're doing that, the size will be in the printer driver already, and your layout just needs to be sized to 12x12 - you will have to trim off the edges...). On the 12x12 paper, you'll get about a 1/8 inch margin all the way around, which you can choose to leave on, or trim off with a paper trimmer.
Epson does in fact have the R1800 that can do a borderless 12x12 print, and that size is built into the printer driver.
Hope that helps!