Do they have value? Probably. I could probably come up with a number, but there is an elephant in the room, which I'll get to in a moment.
Provenance is the most important word in props. "How did you get it?" and "Prove it was screen used." are really important to prop collectors. Proving it came from the Tunisia sets is one thing. Few people are going to take the word of some guy who picked up some plaster bits in the desert. Are they recognizable pieces that can be seen on-screen? You've got the photos, so that's a good start, do they show the pieces in place? Are they from ANH, AOTC, or a later repair or the 2012 restoration? Those answers can make a difference on the value.
Now to the big issue. You say they were "removed" from the homestead. That can be a loaded word. It can mean anything from "removed by the owners due to damage" to "vandalized and stolen". If they were removed with permission, that's one thing... except for the whole ethical argument of damaging an arguably historic site. If the parts just fell off and were collected with permission, I don't think I'd have an issue there. Anything else is a grey area, at least ethically.