In common with the rest of KDE, Konqueror is highly configurable, so you can really get the look and feel that best fits your needs and wishes.
The basic look of Konqueror is homogenous with the rest of KDE, so if you want to change the look of Konqueror you have to change the whole of KDE's appearance. See the documentation of KControl for that, or if you just want to change the window's frame and button style then RMB on the Titlebar and choose the Decoration option.
However, you can change the font and some color options with the appearance tabs of the dialog boxes you get by selecting :
Settings->Configure->File Manager...
or Settings->Configure->Browser...
For the File Manager and the Web Browser respectively.