[FerTheWin]

Post the image? Depending on the current quality of it might be able to be upscaled without much quality loss.

[Pentatonic]

Nop, It won't look good if you increase the w&h.

[SnowCom]

Merge all your layers, hold CTRL and click the image on the left of the layer name, edit, copy merged, new, type in your dimensions, Edit paste, CTRL T, make it bigger, save for web and device then that's it!, hope I helped.