A search on Google Image for "simple forum theme" reveals many designs for your reference. Some of them are well-designed and elegant. To me, it looks like your forum theme went for simple style. Although it is looking simple, it hasn't reached a degree that it could be considered well-designed. Maybe you could try replacing the "OLD" tags with images like how you did it for the "Link to google" subforum, and make the font styles of the logo and other texts more correspondent with each other.