I don't do SL but as someone who also works with making textures for 3D models, having someone who can't seem to understand how difficult it can be to make things line up is frustrating.
Sometimes moving a spot one pixel over makes it become all stretched and warped, sometimes a stripe is going over a seam in the texture, and sometimes the different sections of textures have different pixel dimensions so it can be impossible to make it flawless.
Even if a customer doesn't understand exactly why something is hard to do or just flat out impossible, they need to trust that the professional they hired knows what they are talking about when they say it is not something they can do.