Hmm. Super skinny band, like 2mm or less? If it isn''t already? A bezel? Definitely a halo would do it, of course, like you mentioned, but if you don''t like the look then it''s not worth it. You could get a new peg head (it looks like your setting has a peg head, yes?) and get it set higher, too, if it wouldn''t irritate you to wear.
Also, you can try this trick which I''ve found always works for me- put it away for a week, wear a much smaller stone- a fake if you need to- and when you break out your real diamond it''ll look enormous. (Whenever I have had to have my ring worked on, I wear my other ring which is, like, 2 1/2 cts smaller, and my e-ring seems like a boulder when I get it back!)
BTW your diamond looks plenty big to me- very pretty!