Placing two rocks out in the lawn (if I'm understanding correctly) might look a little odd and random, especially if they are gallon pail-sized rocks - the bigger the rocks, the better. If they are large rocks, it would help to make it look like an intentional design. Even better would be if it was just the beginning of a plan that would increase the size of the bed over time with more rocks and plantings - that would make it look more in scale with your yard, as well. Just my opinion... feel free to ignore it!
