Ideas for more challenge?

Play a higher difficulty level. Crippling isn't much harder, but masochistic is pretty mean.
Turn off tech trading, or leave it on and don't do any trading yourself.
Turn off minor races.
Turn on blind exploration.
Customize your civ to have weird abilities, or no abilities at all.
Don't use any exploits, or tactics that you think are too easy.
Try a different strategy, like cultural conquest.
Play a smaller map with everything set to abundant.
Choose an alignment that's the opposite of your neighbors'.
Restart the game until you get a bad starting location, like a home planet with no bonus tiles and a position in the corner.

just play suicidal with the max opponents on the largest map and you will get your fill of challenge.

Play with your nose.

I think Ohalland's on to something...

The more resources the AI has to work with, the tougher they become. Set everything to abundant. You might try to choose only the good, or only the evil races as opponents and then play the opposite alignment. The one time I chose every evil morality option I was ganged up on by 4 other races and stomped into oblivion within 2 years.

Tough is the setting where the AI plays without any hinderances, or bonuses. After that they start getting at least economic bonuses.

Enjoy

1) Push the TURN button 20- 50 times without doing anything to give the AI a head start.

2) Edit the XML files to make it as hard as you want

Gigantic galaxy on suicidal with everything set to abundant is sufficiently hard enough for me (extremely challenging but with a possibility of winning)

Cheers,
Superconductor

Hardest settings are scattered stars, medium map, max difficulty.

Research etc as your preference.

voluntarily refuse to use 1 specific tactic you find useful, including things like research. if you build no research improvements you will find the game to provide a VERY different(and difficult) experience in most cases.

Yeah, but I hate needing to be that artificial in order to get a good game. Now that 1.2 is out it is much harder to win on the last 3 difficulty settings if you turn off tech trading and avoid any cheesy tactics. I also like Medium Galaxies with everything Abundant. It is kind of like playing a Large galaxy except that everything and everyone is right on top of each other. It sort of maximizes the tension right from the start. And then pick evil against a pack of good races and you WILL find it challenging.

I find Huge maps a lot easier than medium maps, because you have more time and space to develop. Particularly if clusters are set to tight.

9 opponents with medium maps everything abundance is the way it is supposed to be played i think. I almost always play like that.

take off all your ability points at the start.

Apart from cranking up the difficulty, I love playing with self imposed restrictions.

To date I've done:
- single sector - not allowed to own any planet outside your starting sector (giving away any planets which surrender to you)
- protect the minor - must keep the first minor you meet alive... can be v tricky if it is in the middle of another major's area.
- keep every major alive (you need a decent sized galaxy to be able to get to aid people in time before they surrender)
- pacifist - no attacking anyone... you still need a defensive military but you cannot even attack unguarded troup ships.
- trade only - no economic buildings on your planets.
- hive - only tiny and small ships (so you chase up the logistics branch to compensate).

there's must be lots of brainers and/or time here to be able to play the game at varied high difficulty levels.

I finished a normal difficulty level through influence victory, and now I'm trying a huge galaxy at 9 aliens challenging level on patch 1.4. I find the challenging level really tough. Usually some of the AIs have Manufacturing Capital within 6 months or 24 turns, while I was just starting to build one. The only thing I can think of to win in this challenging or higher difficulty levels is to have good start in which you can grab 10-14 planets within a year and slowly build from there.

I sort of cheated because I keep on restarting a new game if I can't get about 10-14 planets before I bump into alien space that hinders my expansion. I must have restarted 20 times before I finally got a decent map to start with. This time I started with 1 solar system in a sector, and expanded from there. I wish I started with 3 solar systems with 3 inhabitable planets each, but this should be fine.

By the way how did you get your medals?

I find the challenging level really tough.

As you flesh out a good strategy it gets more manageable. I remember getting my butt kicked on normal when I first got the game, but now it's a cakewalk at that level. Just practice and listen to the advice given by some of the higher players. It's worth listening to, even if you only incorporate a small portion of it into your own strategy.

I sort of cheated because I keep on restarting a new game if I can't get about 10-14 planets before I bump into alien space that hinders my expansion

I try to go right at the AI players in order to inhibit their expansion. I'll head toward the edge of my range to colonize first, because I can always grab the planets close by a little later before the AI gets that close.

By the way how did you get your medals?

The medals are from playing on the metaverse. Kind of an online highscore list, where you can see how you stack up against others.

Thanks for the reply DethAdder, I'm playing the challenging difficulty, huge galaxy, 9 aliens right now... I've gotten past the steep climb, now it's sort of smooth ride, in terms of nobody really wants to create trouble with me. I have the highest influence in the game, above average technology and economy... But it's becoming more like I can win by influence only (like the last time), but by conquest, technology, I'm kind of lagging... still have to experiment with the conquest victory...