Don't have acces to advance map right now, so I'm afraid I can't check anything for you in advance map, but I can give you some pointers to begin with. First off, get your script editor ready, because is, indeed, going to require you to get the scripting muscles flexing.
First off, go to advance map, and set your script editor of choice as default script editor (I believe that option is found under 'options', but if not, it's somewhere in that top line). Then, go to the script in question (which is, if I'm not mistaken, the script on the pokeballs themselves), and either double-click, or select 'open script' on the menu on the left. You'll get a box with a terrible mess of garbled junk (if you've never seen any script before, that is. Trust me, it starts making sense after a couple days :P) I can't help you on the pictures right now, wouldn't know how to do that off the top of my head, and as I said I don't have acces to Advance map atm. However, editing the text isn't all that hard:
First, you want to, logically, search for the text you want to change. It's going to be in the bottom part of the window, where you'll get a bunch of these kind of things below each other:
Now search for the text for, say, bulbasaur. I've got no idea what it says, but it should be easily found, and once you do, it's really as simple as erasing the text, and replacing it with your new one (you'll need to keep the =, as otherwise it won't recognize your string as text, but for everything else you're free to go). HOWEVER, there is one catch: if you simply replace the text, the new text MUST be shorter than or of equal length with the original text. If not, things are going to get completely messed up, because you'll start writing data to bytes that are already holding other data, which causes really odd things to happen, and just might break it. So, if you're sure your text is shorter than the old one, you're set! Just test it to make sure it all works, and make sure to make use of text-managing commands:\n puts the text after it on a new line, \l scrolls up the previous line and then puts the new line in (remember, the text boxes only have two lines and about 35 characters per line), and last but not least \p lets you open a new 'page' so to say. I can't explain this one that well, but just try it out, you'll get it when you see it. Now, if this was all, don't forget to hit the button called 'compile' when you're done, this will write the changes you made in the script to the ROM (so anything you do before you hit that button has no actual effect whatsoever).
So, what about when what you want to say is longer than the original? Well, don't worry, that just requires a little more work. Step by step:
1. I'm not an XSE user, so I /might/ get the terminology slightly wrong, but I believe it goes like this: put #dynamic 0x800000 at the top of your script. This tells XSE to look for free space large enough to hold all the new stuff, starting at 0x800000 (this is where the empty space on ROMS tends to start, it's actually around 0x740000 I believe, but just to be safe 0x800000 has kind of become the standard) and it is connected to @-signs. If you have #org @whateverisconvenient (seriously though, you just need to make sure that if you have multiple orgs that need inserting, you'll have to make sure to use differnt tags, so your first text is called @text1, the second @text2, etc. Just an example though, it honestly doesn't matter what you call them).
2. Now, change your text (this could also be step one, as the order in which you do these things doesn't really matter, as long as you make sure that the compiling happens LAST). You don't have to pay any attention to length whatsoever this time, as we're going to get you some empty space to put the new stuff in, yay!
3. Now, you'll need to replace all instances of the #org of your new text with @text (or whatever you want to use). Personally, I'd use the find/replace function to do this (I'm going to assume XSE has it...), but you could just do it by hand. Now, make sure to ONLY replace the NUMBER with @text. You'll actually need the #org for your script to work :)
4. If you're sure you've replaced everything by what you want it to be, you just hit that compile button again, and voila! You should get a list of offsets, but in this case those don't matter as you didn't replace the starting offset, and you should be able to just ignore them. If you want to make sure it all worked properly, just close the script and open it again, and you should see the changes you made reflected in the script.
Well, hope this works for ya, if it doesn't, just have a look at some tuts, it really isn't all that hard, just takes some getting into :)