You can always tell the company/group that you will permit them to use (specific photo) for (specific purpose) for (specific cost). But of course, they do not have to accept your offer.
Firstly once you take a photo that photo is yours - the rights are yours and you may do as you wish with it (within limits).
Now firstly there are some times when this is not the case - if you are working undercontract the contract can state that the image rights are transfered to another party - of course you have to sign to agree to that as part of the contract.
Secondly there are some limits on types of photos - for example if you take photos of people where a person(s) are a main subject you need a model release - Beyond that statement the indepth understanding of this area of legalities is very hazy to me so I shall leave it at that.
So provided that you have not written the photo over to someone else or there is not a model release form issue then the photos is totally yours to do what you want with. Now if another party wants to use that photo you are fully within your rights to charge what you will and to put any limits on usage of the image as well.
Typically you want to limit the other parties use of the image to a specific area (that way they dont get free use out of it in other areas). This would all be sorted out in a contract between you and them. Now if they don't agree to your price or constraints then they can't use your image and will have to look for another.
They cannot (legally) use your image without your consent
You can charge what ever you want. This is a complex issue that you and the client will have to work out. Look into their usage, position on the page and expected hits. Also speak to them about the life of the image. Is it one year? Forever? The list goes on and on. We will not be able to give a clear answer until you spill some details.
Love & Bass
The images is basically being used for a conference website so they can show the attendees shots around the Austin Capital. Like tourist information.
I understand that part. Not sure how long the image will run or it's size or placement. How popular is the website in hits? Will you be giving them exclusive rights or a one year deal?
Love & Bass