The texture has to be oriented along the axis of the loft. Usually that's up-down. The texture appears to be oriented the other way on the left (longer) pipe. The other (shorter) pipe looks like the texture is excessively tiled around the pipe circumference, though it's hard to tell.
From top to bottom as viewed in your paint program, your texture should represent an object that's the same length as your loft cross-section model. Thus if your 3DC cross-section model is a pipe that's, say, 10 m long, the texture should depict the appearance of a 10 m length of the pipe. For an object such as a pipe with a circular cross section, the width of the texture should represent the variations, if any, about the pipe's circumference, and usually no more or no less than that. Here's an example:

Remember that the texture will be repeated/tiled along the length of the loft, so the top and bottom of the texture should match to give the pipe a continuous, seamless look -- unless you specifically want seams representing, for example, welded joints. The same goes for the left and right sides of the texture where it wraps around the pipe. Some paint programs have an "offset" tool that relocates the texture by an adjustable amount along either or both axes. After applying the tool, it should be immediately apparent if there are visible seams in either direction. You can use the paint program's "clone" tool to disguise these seams.