Congrats on finishing the 25 Texture Challenge (I'm also in the process of doing that)!

Things You Did Well:

1. It looks like you really took your time with the direct texture studies, which is great! It's very important to be patient with this, and to be constantly referring back to the reference every 4 seconds or so. Though I can't tell whether or not you were doing that last part, make sure you're doing it whenever you're studying something!

2. For most of these (I'll point out some of the exceptions in the "Things to Improve" part), you did good ensuring that you were focusing on the cast shadows of the forms, rather than the forms themselves, as is apparent when you do your texture gradient. Though I do feel that many of the texture gradients could use some work, that's something that will come with practice as you get better at identifying cast shadows.

Things To Improve:

1a. In quite a few of these, it seems that you're drawing patterns or objects, not textures. With #18, the basketball, the big empty cross in your direct study should not be pure white unless there was a ton of light shining on it (if that was the case, my bad). It's likely some funky, hard to understand texture, which I find to be the case with shiny textures. I believe Uncomfortable constructs a beetle in one of these lessons, and he makes it look shiny, which may be the kind of texture you're going for there.

1b. Additionally, in #24, "glass shards" isn't a texture, it's moreso a collection of objects, of which you outlined the forms instead of identifying cast shadows. The texture in that image would be on the glass shards themselves, and would include things like scratches, divots, shiny-ness, etc.

1c. This is the case for a couple more of these, like #5 (in which you did good identifying the textures on the pieces of wood, but made the mistake of assuming the individual rectangles were part of the texture), #2 (same case as with #5), and maybe #19? I haven't observed a straw hat in a while, so that one might be fine.

Conclusion

If you want, you can redo 3 of the textures (specifically the ones I called out) to try and apply the advice I gave you (though whether or not you do that is up to you), but otherwise, just make sure to focus on identifying the cast shadows of textures instead of drawing the forms themselves. I recommend that for the constructions you'll be doing in each lesson you go the extra mile of adding texture (when allowed to) just to get some extra practice, and so you can get a feel for applying texture to 3D objects.