The Collaborative International Dictionary of English v.0.48:

Sunshiny \Sun"shin`y\, a.
   1. Bright with the rays of the sun; clear, warm, or pleasant;
      as, a sunshiny day.
      [1913 Webster]

   2. Bright like the sun; resplendent.
      [1913 Webster]

            Flashing beams of that sunshiny shield. --Spenser.
      [1913 Webster]

   3. Beaming with good spirits; cheerful. "Her sunshiny face."
      --Spenser.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "sunshiny":
   aestival, aglow, beaming, beamy, blood-hot, blood-warm, blushing,
   bright and sunny, burning, calid, candescent, clarion, clear,
   cloudless, equatorial, fine, flushing, genial, gleaming, gleamy,
   glinting, glowing, illuminant, incandescent, irradiative, lamping,
   light as day, luciferous, lucific, luciform, luke, lukewarm,
   luminant, luminative, luminiferous, luminificent, luminous,
   lustrous, mild, orient, pleasant, radiant, rainless,
   room-temperature, rutilant, rutilous, shining, shiny, starbright,
   starlike, starry, streaming, subtropical, suffused, summery, sunny,
   sunshine, temperate, tepid, thermal, thermic, toasty, tropical,
   unfrozen, warm, warm as toast, warmish