Please don't use Blender, or Gimp, or any other free program.
I disagree with this for a few reasons.
First off, different programs excel at different things. For high quality animation and rigging, Maya is the best, no arguments here. A friend of mine moved from Blender to Maya as he's animating for films, and he's never looked back. However, Blender and 3DS Max are known to have better, faster workflow for pure modelling, especially for architecture and the like. That's hugely relevant for level design in games. Additionally, Blender is getting a new real-time rendering engine called Eevee (no, not the Pokémon :V) in Blender 2.8 that will be replacing Blender Internal. Maya on the other hand is pretty limited in that regard (you can get real-time rendering but I hear it's awkward to do and not really worth the hassle as it's subpar). The benefit of real-time rendering is of course speed, as it allows you to see what your animations look like in a "production" state much more quickly.
Blender also has the benefit of being open source. That means anyone can develop their own code and give the program new functions. This means Blender is the best for making it do EXACTLY what you want if closed-source programs like Maya don't prove good enough for certain tasks and you think you can write code to make Blender do better. Someone may have already written that code for you, and installing new scripts is easy. Even if you primarily use Maya, this can be really useful since porting projects back and forth between Blender and other programs is easy, so you can port your project to Blender, make it do what you want, and port it back to Maya to continue or use that mesh in the finished animation or what have you.
Obviously this message isn't directed at you on a personal level. If you're using Maya and you feel it's all you need for your purposes, then more power to you, I'm definitely not here to tell you that you shouldn't use Maya. And you're right in that Maya is the one that the industry juggernauts are using, meaning if you want to work for them specifically as a game's artist, you should focus on Maya. But I think everyone should research each option and see which one (or more, as some people need more than one program) is best for their purposes, which is why I think it's not a good idea to tell people not to use other programs. Ideally, you should have all of the best ones installed and train yourself a bit in all of them, even if one of them is your main one.
However, I will agree with you 100% on ditching GIMP for Photoshop. Photoshop, especially in combination with Illustrator, is just objectively better than GIMP. It does the same thing but way better and easier. When I was in a course last year, they were trying to train the class in GIMP. It took them over 20 minutes to do something in GIMP. It took me 2 minutes on my laptop in Photoshop.
And I'll say this to you personally. If you want to be a games artist, apply to Gnomon. I'd be glad to look at your portfolio and tell you what they look for in applicants. Gnomon is the only art school in the world that will actually prepare you for this field, and it's worth every cent. Each year they have between a 97 to 100% job placement rate, and these aren't just average jobs, these are the big name jobs people actually aspire to get when they choose to enter this field.
I'm not specifically looking to be a games artist. I want to make my own games, or at least play some role in mechanics and level design on someone else's game. Main thing I want to train myself in is level design theory and learning the likes of UE4 and Unity at the moment (that's also why I'm learning to mod games such as Sonic Generations, to give myself a hobby in the field too), though 3D modelling and image editing are probably the best strengths I have at the moment as they were the least limited skills by the laptop I had for the last four or five years. They will also be very useful for learning level design.
I will read up on Gnomon later though, thanks for the tip.
For now, though, 10 minutes to Sony's E3 conference. Let's see what they've got. :V