Another reason I forgot to mention to keep things up is to get feedback from multiple people and then use it to improve your design.
With that being said I wanted to give you feedback and tell you the background itself is very nice and clean, the social buttons are also very nice I love them however their backgrounds are very flat, and do not compliment them well. They need to feel more 3D less flat and a bit less simple. The black outlining on them is also meh to me nothing ever needs a thick black outline, sometimes a thin one will compliment things well but a lot of times a thin darker color (not black something more complimenting dependent on the design) to give it just a bit more depth. The login box is almost there, the line work needs to be more sharp, when you free hand things people shouldn't be able to tell it's free handed and if that's something you struggle with try sketching it first then going over it with the pen tool and using the pen tools shape rather than your free handed "rough draft". This will make your curves look more natural/lines in general look more natural. Good work on drawing half of it then duplicating and flipping it as it seems you have done to keep things even on both sides. It is also very simple and could use some kind of texturing or background. You can use anything as a texture, set it to overlay what you are using, make it a clipping mask over what it's to be texturing and then change opacity till it looks good. Texturing might bring it enough depth but again maybe not so you may have to do so more effects on it to make it look more 3D feeling. You also made the black outlining really thick once again refer back to what I said before about doing this. The text on this needs a shadow as well and I suggest downloading the runescape font and using it to make it feel more authentic to a login screen. To create a shadow just like the client does in-game you simply use an all black text behind the original and move the background text 1px to the right and that's it. Even if you don't use the runescape font then still do this for any font used for these kinds of texts it just sets them off and makes them more readable. Lastly the logo, it needs to be a lot sharper this looks like a major rough draft and I'd also strongly suggest creating some kind of background behind the logo to help set it out from the background and to help you easily create more depth using the logo's background. The background if you made it looks so good that it looks like one guy made the background and someone else made the other stuff (other than the social icons those are on point very nice job as well). When one thing is that much better than the others this also makes other things look better and worse than what they actually are so try to keep up the standards with everything throughout. I hope you enjoy this feedback and I know you probably already are aware of a lot of this stuff but hope it helps anyways. Peace bud.