You have an interesting situation. Does it get any direct natural sunshine on that wall? Let us say you 4hrs of direct sun coming through windows then you want to make use of that. You will be hard pressed to beat that intensity. I would probably think of say 4 ft 4-6 bulb led tubes suspend from top and angled towards the plants say at 45 degree angle and say 6-8 inches away from the plants. If you adjust it correctly you can still not shadow the direct sun.

Thank you for responding, @tropicofcancer. The fixture will be an in an open floor plan room that gets a lot of low grade ambient light, and there's not much I can do about that, nor can I obstruct the windows with the apparatus. I've tried growing indoors before using natural sunlight several times, and there's just not enough intensity. I was thinking along the general lines of what you suggest in terms of placement. Do you think LEDs will be enough for herbs? If so, do you know of any brands that have a "natural" looking spectrum (I know that's subjective) in roughly the wide and thin bulb shape I'm describing, and where I can get a close-fitting, but wide angle reflective shield? The product lines from the online grow light manufacturers I've come across seem geared mostly to larger greenhouse and hydroponic setups, where whole rooms can be dedicated and high yield is paramount - not the lesser strength, more aesthetically appealing approach I had in mind. Thanks again for your help.

I missed the aesthetically pleasing part. There is a company that manufactures showroom style led grow lights that fits the bill most closely. The name just escapes my mind right now. They are expensive - like $100 per fixture or so.

Most grow lights or any fixture adapted for growing is going to look "industrial". But here is what you can try: Avoid full spectrum red/blue type grow lights. They have this awful purple color. Aim for high CRI daylight type lights. 3500K-4000K lights will look more natural and still have enough blue in them for leafy plants. Any higher it will look harsher bluish coloration. If the lights are going to far away from the plants you are better off looking for higher wattage and more focussed beams of lights.

I know I did not fix your issues but hope that helps.

I would say an MH grow light (Metal Halide) would be the best type for your situation. Here's a pretty useful article explaining:

http://www.htgsupply.com/informationcenter/resources/hps-grow-lights-vs-mh

TL;DR

This gives off less 'red' light, and more closely matches the spectrum natural light has. Also, the article specifically mentions this type being good for herbs :)

Hope this helps.

I grow with HID's & agree with Brian. They really pack a punch & are well worth the $$.