The character resembles a Valkyrie (maybe because of the helmet with wings?) but I like the design and the character's pose, so powerful and mysterious. The blending of the background colors and the designs, especially the wings, are done beautifully. Overall this work is excellent!
Things to improve? Hmmm, I don't see much to improve because this artwork itself is great, but I think it would add a dangerous yet mysterious aura/effect to the character if you make the two swords look very sharp, deadly and dangerous (maybe add or have this gleaming and glowing light effect) since the character portrays a strong and brave Angel, or warrior perhaps.